A LD rangefinder is designed which has the characters of low cost, reliable and high performance to price ration. Optimal design of the laser rangefinder is discussed according to the system’s applied demand, optical system,laser transmit driver circuit, laser detection circuit and signal process software. The laser rangefinder used in automobile crashworthy system can get 150m measurement range and ±1m measurement accuracy easily, and improve security of drive and ride effectually, which confirms that the laser rangefinder is practicable.