For the disadvantages of high error of time measure, low precision of range-finding and small range in the laser range-finding system, a high precision and long range laser range-finding system based on delay line interpolation method is designed. The operation principle of the system is analyzed. The hardware and software algorithm designs of the system are introduced. The high precision time measure unit of the system is introduced. And a high precision and long range laser rang-finding system is developed. Experimental results show that the system is feasible, stable and reliable and has a greater prospect.