As a typical form of cloud-native application, microservice architecture has been widely used in various enterprise applications. In enterprise practice, many microservices are formed by decomposing and transforming the legacy system of monolithic architecture. The decomposition decision, especially database decomposition, has a great impact on the quality of the microservice system. At present, the microservice decomposition decision mainly depends on the human subjective experience. The whole process is costly, time-consuming, and uncertain. To solve this problem, this study proposes a scenario-driven, bottom-up microservice decomposition method for monolithic system. This method uses scenario-driven method to obtain the method call and database operation information of monolithic system by dynamic analysis, and to generate database decomposition scheme based on analyzing the association among data tables, and then it searches from the bottom up to generate the corresponding code module decomposition scheme. Based on this method, this study implements a prototype tool MSDecomposer, which visualizes the decomposing process and supports feedback adjustment strategies of multiple dimensions. This study conducts case studies based on several open-source software systems, and the results show that the method proposed in this study can significantly speed up the decision-making of microservice decomposition, reduce the decision-making burden of developers and the final result is reasonable.