The invention provides a combined Web service selection method based on transaction and QoS. The method comprises the following steps: firstly entitling transaction property to Web service, and then analyzing a combination problem of services with transaction property requirements; analyzing a performance problem of combined services with transaction attributes; and finally providing the combined Web service selection method based on the transaction and the QoS according to the performance comparison of the transaction combined services; the method specifically comprises the following steps: first step, when current component service is selected, obtaining candidate component services satisfying the transaction property requirements according to the transaction features of the component service that has been selected and according to the rule requirements of the transaction combined services; second step, performing performance estimation on each candidate component service, wherein the QoS and the transaction property requirements are considered in the evaluation; and third step, repeating the above processes until a combined service satisfying the requirements is obtained. The technical scheme provided by the invention has good selection accuracy, and has better feasibility and validity.