A three dimensional structural testing system for static and pseudo dynamic test is developed, in which a coordinate system has been used in the measurement. The center of the ball joint hinge in an almost neutral position for the displacements of three actuators was the origin. However n process since the initial error cannot be controlled. This makes it difficult to exactly compare the results for different coordinate systems though the error is small. In this paper, to eliminate this difference, we set up a new coordinate system with the origin being the point of absolute zero of the actuator displacements. Since the origin usually cannot be measured directly, the new coordinate system is determined by appending three unknowns and a set of equations at the origin. The transformation between the new coordinate system and the previous one is obtained using a shift and Eulerian angles.