In this paper, a kind of semi-flexible valve piezoelectric pump is designed according to the structure of venous valves. The change between the valve and valveless state of the piezoelectric pump can be achieved, because the driving end of the piezoelectric oscillator is controllable. Firstly, the structure and the working principle of the piezoelectric pump with half flexible valve are introduced. Then the valve body is analyzed theoretically, and finally the experimental prototype is fabricated and tested. The experimental results show that when the drive voltage is 220V and the frequency is 7Hz, the inlet and outlet pressure difference of the half flexible valve piezoelectric pump can reach 199 mm. When the drive voltage is 220V and the frequency is 11Hz, the experimental flow of the half flexible valve piezoelectric pump is 44.5ml/min. With the increase of the driving voltage, there is a single peak and double peak in working frequency and flow rate results, respectively. The research proves that the half flexible valve piezoelectric pump has the function of pump and can realize the conversion of valve and valveless state, verifying its validity and theoretical analysis correctness.