Indoor simulation test systems and their key technologies used in laser warning were investigated. After simulating the actual environment, a simulation test system was established for laser-guided weapons. Firstly, the composition of the simulation test system was introduced, then, by taking the case of laser coding recognition test for an example, the simulation test methods based on receiving diffuse reflection were discussed and the key factors in the simulation test were specially studied, such as the calculation of laser energy, and the position calibration and energy analysis of diffused screen. Finally, a recognition test of laser pulse code was performed by the diffused laser signal with a pulse energy of 10 mJ. Obtained results show that the detection probability reaches 100%, which proves the feasibility of the simulation test system.