A three-direction piezoelectric sensor parallel-type balance with four supporting points was designed for the dynamic load measurement of the all-movable rudder which withstands high-load and installed in narrow space. The piezoelectric quartz was selected to be the force sensing element, the spatial layout and measuring principle of this three-direction force sensor with four supporting points were discussed and the calibration method of parallel balance was studied. Static calibration and compound loading test were carried on this parallel balance. The generalized inverse static decoupling algorithm based on the solution matrix of calibration matrix was used to decouple. From the view of equivalent application points' offset, the error generation mechanism of parallel piezoelectric balance was analyzed using ANSYS finite element software. The experimental results showed that the maximum nonlinear error and repeatability error of the balance were 1.352% and 1.019% respectively. The largest interference coefficient was 2.865%. The influence of composite load on vertical force measurement accuracy was less, yet on the bending moment was obvious. The balance static calibration indexes satisfied the test precision requirements. However, due to the different effects of different load on the range interval between sensors and the superimposed impacts of the composite loading time interval, the balance measurement accuracy was reduced and not satisfied multi-directional load measurement.