The network platforms provide free products to one side, which makes the SSNIP test based on the change of price nullified to judge the relevant market. Taking the video platform for an example, based on the SSNIP model of Twosided Networks built by Filistrucchi, this paper improves the traditional SSNIP test and builds a SSNDQ model of free products in Twosided Networks by increasing the ads time instead of raising the prices of goods. On that basis, it adds the subscription revenue to the improved model for further analysis. The main conclusions include as follows: (1) Although the traditional SSNIP is not applicable for free goods, the ads time is an effective substitute variable for price in SSNIP test because it can affect user's “Attention” to lower the quality of products. This paper proves that the improved SSNIP is general and gives the judgement condition of defining relevant market based on SSNDQ test. (2) Giving a complete method and analysis framework in market definition on free products of network platform firm and the situation which free goods and goods with prices coexist under a trend which consumers pay for the platform, it infers users' different behaviors and conditions of judging the relevant market under different results of profit difference. The test based on the above methods can provide evidences to M&A reviews and antitrust determination.