The traditional laser range finder cannot meet the need of real-time and the measurement accuracy. Owing to this, a multi-frequency modulation laser range finder system was designed based on orthogonal calculation and CORDIC phase solver. An improved orthogonal algorithm was used to calculate the tangent of the ranging phase for noisy environments, and the angle was calculated by CORDIC angle solver algorithm. The proposed algorithm effectively improved the range accuracy and greatly reduced the computational. In experiments, the sampling frequency of AD converter is 500 MHz, the SNR is 14 dB, the word length is 16-bits, the measurement range is 150m, the phase difference resolution is better than 0.026 4° and the distance accuracy is better than 0.11 mm.