In the singlepath pointdiffraction threedimensional measurement system with only one fiber pair, the measurement accuracy in the lateral direction parallel to the fringle direction is poor. To solve this problem, a dualpath pointdiffraction interference system is proposed to enhance the accurate threedimensional measurement in this study. The influence of pointdiffraction wavefront error, structural layout of measuring probe and threedimensional iterative reconstruction algorithm on the threedimensional measurement accuracy is analyzed. Based on the analysis, the optimal system parameters (e.g., pointdiffraction source structure and structural layout of probe) are determined. The experimental results show that the accuracy of the singlepath pointdiffraction interference system for threedimensional measurement in the x and y directions are in the order of submicrons and microns, respectively. In comparison, the dualpath pointdiffraction interference system can reach the order of submicrons at three directrions. The feasibility and accuracy of the proposed system are verified. It provides a feasible method for the measurement threedimensional displacement and size without guide rail.