Abstract: The terrain matching guidance system equipped with radar altimeter has low detection precision and is susceptible to electromagnetic interference. Moreover, it can not work over the sea. In order to resolve these problems, a scheme of laser altimeter is designed to take the place of the radar altimeter. The technology of diode-pumped solid-state laser is adopted to design laser transmitter, outputting infrared/blue-green dual-wavelength laser. The altimeter with dual-wavelength output can detect both the land terrain and the seabed terrain. To promote the performance of the laser altimeter, the detectors are selected carefully, and the optics system, the scanning system and the signal processing system are designed optimally. The designed laser altimeter features small size, light weight,