According to characteristic of strap-down seeker for individual weapon, a guidance law combing proportional guidance with body-tracking guidance was proposed. By using the error angle signal output of the seeker and the attitude signal from the posture gyro, the angular rate of the line of sight was obtained through differential network. The proportional guidance and the projectile tracking guidance were completed with input of the angular rate and the error angle signal for the autopilot. Besides, an elucidated design method for the autopilot of root locus method was given and general feature of the autopilot were also analyzed. The rationality of the new guidance law and the design method of the autopilot was verified through mathematical simulation. High hitting accuracy can be realized and good dynamic characteristic was gained. Finally, in order to demonstrate the feasibility of MEMS gyro and inertial gyro, a hardware-in-the-loop experimental scheme was presented for further demonstration of the design.