A novel 3D precision displacement system of large travel, nanometer level and displacement measurement by itself is developed to satisfy the need of precision displacement. The system is designed with a modular structure, in which the driving mechanisms of three directions adopt the same design structure and calls as X direction, Y direction and Z direction 1D worktables, respectively. The dual-stage actuators of coarse and fine driving have been applied in the precision displacement system in X, Y and Z directions and three sets of metrology gratings are installed in X, Y and Z directions respectively. In every direction,the AC servomotor combining with a precision lead screw and a linear guide is used to actuate the coarse driving,and a piezoelectric micro-displacement actuator combining with a flexure hinge is used to actuate the fine driving and then a set of metrology grating is set for the displacement measurements of the coarse driving and fine driving. Therefore the need of large travel, nanometer level and displacement measurement by itself of the displacement system can be satisfied. The structure design of the displacement system is introduced and the displacement resolution, measuring principle and the motion performance of this displacement system are also analyzed in details. Experiments indicate that the displacement difference between actual and setting are no more than ±0.030,±0.028 and ±0.033 μm respectively in X, Y and Z worktables in a range of 40 mm, which verifies the effectiveness of design of the displacement system and provides the theoretical basis for its development.