Objective In order to obtain the mechanical properties of the heart valve,a high-precision biaxial tension machine system was designed. Methods The system adopted the structure of upper machine and lower machine.The host computer used Labview software programming, the man-machine interface was designed and enhances the flexibility and the data processing ability of the system . The lower computer supported NC language programming and improved the simplicity and flexibility of user programming.The system used the mechanical motion hardware module with sensitivity of 1μm,16-bit data acquisition card,optical displacement measurement, and improved the accuracy of the system measuring stress and strain.In this paper,the mechanical properties of porcine mitral valve were measured by biaxial tension, and the results were compared with those of the foreign counterparts. Results The difference was between 0.4%-3.7%. Conclusion The experimental system can flexibly test the mechanical properties of heart valves and other biological soft tissues.