In recent years, social application with shopping has become an indispensable activity in people's daily lives. A number of previous studies have investigated various risks in online shopping and consumer's belief. However, few scholars paid more attention to buying behavior, especially on consumer's cross-platform buying behavior. Although consumers can purchase goods directly in platforms that have given them information, they also buy target products on other platforms. This study conceptualizes and implements concepts such as perceived risk, trust, negative reports, and consumer cross-platform buying behavior. A questionnaire survey of users ( = 366) was conducted, and a basic description and comparison of consumers' cross-platform buying behavior were made in terms of consumers' perception of the risk of product effects, consumers' perception of service risks, and consumers' perceptions of other risks. The degree of trust in the platform and negative reports about the platform also affect cross-platform buying behavior. As a result, these findings are discussed and explained, and some reference is provided for related platforms. Besides, the study's finding concerning consumer's buying behavior depends on the security of platform in people's conceptions.