In laser guided weapon hardware-in-the-loop simulation, laser energy is controlled accurately to simulate the laser energy in battlefield environment. In order to assure simulation reliability, simulating error should be analyzed. The laser signal transmitting process was analyzed, and the energy control uncertainty of every transmitting link was introduced. The laser energy simulating error model was developed and error analysis method was introduced by an example. The error model can be used to evaluate laser energy simulating error and to optimize simulation design, which can assure hardware-in-the-loop simulation result precision.