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.

平台企业对单边提供免费品，使基于价格变动的SSNIP测试法无法用于判断相关市场。本文以视频平台为例，基于Filistrucchi双边市场测试法，通过将SSNIP测试法中对一边市场的产品价格提升替代为广告时长的增加，改进了基于价格变动的假定垄断测试法，构建了网络平台企业免费产品的SSNDQ模型。在此基础上分析了加入会员收入的情况。主要结论是：（1）虽然传统的SSNIP测试法不适用于免费产品，但是影响用户“注意力”的变量“广告时长”能降低产品质量，是SSNIP测试法中价格的有效替代变量。本文证明了改进的SSNDQ测试法具有一般性，并给出了基于SSNDQ测试法的相关市场判断条件。（2）给出了界定网络平台免费产品相关市场的思路和分析框架、平台付费化趋势下免费产品与付费产品共存状态下的情形，并推导出不同利润差结果下判断平台用户不同行为及相关市场范围的条件。基于这一方法的测试为并购审查和反垄断认定，提供了依据和证据。