A new method of laser ranging is developed by employing a dual-mode photon detector to meet the large dynamic range of the echo photons. A single detector based on Si avalanche photodiode（APD）is operated between the linear mode and the Geiger mode by adjusting the bias voltage on APD and the detected dynamic range of the average photon number is 1~105 per pulse. The 30 m indoor and 500 m outdoor ranging experiments are carried out in the linear mode and the Geiger mode, respectively. The echo signal is recorded by a time correlated single photon counting equipment to investigate the ranging time characteristics in the dual-mode ranging system. The results indicate that the ranging system with a single detector can conveniently switch the operation mode to adapt to different ranging distances and environmental conditions and realize the large dynamic range detection. The measurement accuracy and the detection background noise are further studied while the operation modes are switched under different APD bias voltages.