The base principle of spatial forword intersection is analysed and some relative mathematical models are established. The measurement accuracy of this method is severely detected in lab and the testing results show that the spatial forword intersection is a kind of high accuracy and noncontact measuring method. At the same time, the principle of the positional measuring systems is briefly discussed and the application of the method of spatial forword intersection in the testing process of the testing system of position is probed into, and the testing steps and disposed results of testing data are provided.