Abstract: According to the characteristic of laser guided weapon, a hardware-in-the-loop simulation (HILS) model for guidance and control system was founded. Then, all kinds of errors impacting on simulation system, especially geometric error, were analyzed, and a guidance model with error was created. Through the mathematic simulation, the maximal angle error was given to limit miss distance within allowable range. In order to correct the geometric error, a model of HILS was developed for seeker to track a certain laser spot on curtain. Using the obtained results, nonlinear over determined equations of error parameters were established. With combination of Newton iteration method and weighted least square method, the error parameters were solved and geometric model was corrected accurately. The results indicate that this approach has achieved exceptional accuracy and reliability, which is significant for next phase of HILS.