Abstract In order to carry out biaxial tensile test, a PC-based control system and a digital PID controller was designed and developed on the basis of the three axes loading machine made and PID control principle. And some key techniques in biaxial tensile test have been solved, such as the displacement synchronous control of the same axial jaws, the proportion and non-proportion loading control for displacement of different axial jaws. The accuracy analysis of system shows that the test system has high accuracy and reliability.