The process of using the traditional WordNet Application Programming Interface (API) is based on the file operation, so each execution of API in WordNet library would lead to serious problem of time-consuming in process of text analysis and similarity calculation. Therefore, the improved solution of WordNet API was proposed. The process of constructing semantic net of WordNet concept was transferred into the computer memory; meanwhile several APIs which were convenient to calculate the similarity were added. These improvements would accelerate the process of tracking the relationship of concepts and text similarity calculation. This solution was already applied in the process of Mashup services discovery. The experimental results show that the use of improved API can effectively improve the query efficiency and recall of Mashup service.