Abstract: Null compensation interferometry is the primary testing method for the manufacture of ultra-high-precision aspheric mirrors. The crosstalk fringes generated by stray light in interferometry can affect accuracy and potentially prevent the testing from proceeding normally. Position errors include the decenter error, tilt error, and distance error. During the testing process, position errors will impact the testing accuracy and the crosstalk fringes generated by stray light. To determine the specific impact of position errors, we use the concept of Hindle shell testing of a convex aspheric mirror, and propose the simulation method of crosstalk fringes in null compensation interferometry. We also propose evaluation indices of crosstalk fringes in interferometry and simulate the influence of position errors on the crosstalk fringes. This work aims to help improve the design of compensation interferometry schemes, enhance the feasibility of the design, reduce engineering risks, and improve efficiency.