We are developing a new active three Dimension (3D) laser range imaging system based on a pulse light-source and a modulated receiver (PLMR). A double-frequency YAG laser emits light pulses, which are expanded to light cones, with a frequency of 60Hz. A light pulse can illumine a full scene and a modulated image intensifier micro-channel plate (MCP) selects the reflected light with proper optical imaging devices. A Charge Coupled Device (CCD) receives the MCP output signal and generates an intensity image, and two modulated avalanche photo diodes (APD) collects the light splitting from the light pulse as correct intensified values for the intensity image. The system generates a 3D image, which needs a minimum of two different intensity images. These intensity images are obtained with or without illumination of light pulse and with different modulation applied to the MCP. The above imaging times are equal and relate to detection range. We present the best combination of the modulations and illumination conditions, in the meaning of minimum variance, and the relative theoretical analyses. Detection range, measurement resolution and scan frame rate of the system are given considering the influence of background light and circuit noise. Comparing to other 3D imaging systems, our system has the advantage of achieving both long measurement range and high spatial resolution. Potential applications to industry and military of the 3D laser imaging system are also presented.