This paper focuses on the embedded laser target simulation system based on RTX(Real Time Executive).This system completes the seeker test mission mainly by means of simulating the process of the missile from launch to hit the target through controlling the Laser spot. The system is consisted of upper computer, spot energy adjustment and spot size adjustment. The whole system realizes continuous and rapid adjustment to the energy and size of the spot via the RTX embedded computer system sends control commands to each controller of two units simultaneously. The unit of spot size adjustment: the controller controls the movement of the leading screw and then the leading screw controls the shift of the lens. The motor which controls the movement of the leading screw is direct current torque motor. The unit of spot energy adjustment: According to the Lambert law, the structure uses two crystals that the wedge angles are exactly the same. The system controls the motor to change the relative position of these crystals and then changes the thickness of the optical path crystal to adjust the laser spot energy. This system utilizes RTX embedded system to send control commends s in real time, a share memory area is opened for exchanging the simultaneous data between Windows and RTX. The real-time performance of the whole system has a significantly improve by using RTX embedded system, the system response time reduces to 1ms。Thus the laser target achieves rapid changing which seeker test requirement.