As filed with the Securities and Exchange Commission on October 22, 2010

Registration No. 333-167564

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

Amendment No. 6

to

Form S-1

REGISTRATION STATEMENT

Under

THE SECURITIES ACT OF 1933

INPHI CORPORATION

(Exact name of registrant as specified in its charter)

3945 Freedom Circle, Suite 1100

Santa Clara, California 95054

(408) 217-7300

(Address, including zip code, and telephone number, including area code, of registrant’s principal executive offices)

Young K. Sohn

Chief Executive Officer and President

3945 Freedom Circle, Suite 1100

Santa Clara, California 95054

(408) 217-7300

(Name, address, including zip code, and telephone number, including area code, of agent for service)

Copies to:

Approximate date of commencement of proposed sale to the public: As soon as practicable after this Registration Statement becomes effective.

If any of the securities being registered on this Form are to be offered on a delayed or continuous basis pursuant to Rule 415 under the Securities Act of 1933, check the following box.  ¨

If this Form is filed to register additional securities for an offering pursuant to Rule 462(b) under the Securities Act, please check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.  ¨

If this Form is a post-effective amendment filed pursuant to Rule 462(c) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.  ¨

If this Form is a post-effective amendment filed pursuant to Rule 462(d) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.  ¨

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer or a smaller reporting company. See the definitions of “large accelerated filer,” “accelerated filer” and smaller reporting company in Rule 12b-2 of the Exchange Act (check one):

The Registrant hereby amends this Registration Statement on such date or dates as may be necessary to delay its effective date until the Registrant shall file a further amendment which specifically states that this Registration Statement shall thereafter become effective in accordance with Section 8(a) of the Securities Act of 1933 or until the Registration Statement shall become effective on such date as the Commission, acting pursuant to said Section 8(a), may determine.

Explanatory Note

This Amendment No. 6 to Inphi Corporation’s Registration Statement on Form S-1 (Registration No. 333-167564) originally filed with the Securities and Exchange Commission on June 16, 2010, as amended by Amendment No. 1 filed July 21, 2010, Amendment No. 2 filed August 13, 2010, Amendment No. 3 filed August 31, 2010, Amendment No. 4 filed September 24, 2010 and Amendment No. 5 filed October 21, 2010, is being filed solely for purposes of amending the exhibit index to include Exhibit 10.14, which Exhibit 10.14 is also filed herewith. No changes have been made to Part I or Part II of the Registration Statement other than Item 16(a) of Part II as set forth below.

Part II

INFORMATION NOT REQUIRED IN PROSPECTUS

(a) Exhibits

II-1

II-2

SIGNATURES

Pursuant to the requirements of the Securities Act of 1933, the Registrant has duly caused this Amendment No. 6 to the Registration Statement to be signed on its behalf by the undersigned, thereunto duly authorized, in the City of Santa Clara, State of California, on the 22^nd day of October, 2010.

Pursuant to the requirements of the Securities Act of 1933, this Amendment No. 6 to the Registration Statement has been signed below by the following persons in the capacities and on the dates indicated.

II-3

Exhibit Index