摘要： 微软案、谷歌案与百度案皆反映出在反垄断司法实践中，相关市场的界定总是与不确定性结伴而行。对传统产业相关产品市场界定的需求替代法与供给替代法，由于无法充分反映互联网企业产品或服务所具有的双边市场的特点，因而将其适用于互联网产业反垄断案件时存在问题。要解决这个问题并突破反垄断法实施过程中认定互联网产业垄断行为的瓶颈，不能沿袭传统方法，也不能完全束缚于反垄断法规定，而应该从互联网产业双边市场的特性出发，客观对待互联网企业所提供产品（服务）功能的差异，基于利润来源确定相关市场的范围，并考虑双边市场的交叉网络外部性对垄断力量的传递效果。

关键词: 互联网产业, 双边市场, 相关市场界定, 交叉网络外部性

Abstract: The Microsoft case, Google case and Baidu case all reflect the inevitable uncertainty to define the relevant markets in internet industry in many countries’ antimonopoly judicial practice. Demand substitutability method and supply substitutability method are always being applied to define relevant markets in transitional industry,which cannot incarnate the two-sided markets characters of internet products or services, thus when they，applied to define relevant markets in antimonopoly case, there are several obvious shortcomings. To make up these obvious shortcomings and to break through the bottleneck of defining relevant market in internet industry, we should neither copy the traditional methods, nor be completely bound by the provisions of the Anti-monopoly Law．We should take into account the two-sided market characters of internet industry, treat the different functions of different internet products or services objectively, define relevant markets from the perspective of profit sources, and we must consider the transferring effect of cross-group network externality in two-sided markets to monopoly power.

Key words: Internet Industry, Two-sided Markets, Defining Relevant Markets, Cross-group Network Exter-nality