A new type of binocular vision system was designed used common CCD cameras. Because of positioning accuracy is not high, the experiment used the modified projection algorithm to get the position messages. This algorithm joined the explicit-implicit distortion correction method in the projection algorithm. After correction, the positioning accuracy of the whole system was improved. The experimental results showed that: In the range of 2600 mm, three direction errors in the world coordinate axis Xw, Yw, Zw are 0.200 mm, 2.300 mm and 35.432 mm. Comparing projection algorithm, the errors of the improved positioning algorithm are smaller. The new method can satisfy the system accuracy requirements.