Abstract: A pixel readout circuit was presented and designed for Geiger-mode avalanche photodiode (GM-APD) array applying to laser 3D imaging. Based on the principle of time-of-flight (TOF), the pixel readout circuit consisted of two main parts:active quenching circuit (AQC) and time-to-digital converter (TDC). The adopted TDC was a two-segment coarse-fine architecture to manage a trade-off between clock frequency and temporal resolution. Based on interpolation technique, the LFSR used for coarse counting and the delay-line type TDC used for fine counting achieved a wide dynamic range up to 18-bit together. Meanwhile the clock frequency used in those two parts were reduced to 250 MHz and 50 MHz, which are 1/20 and 1/10 of the conventional design frequency, respectively. Thus, the difficulties of design and applications were reduced significantly. The circuit was designed with SMIC 0.18 m process. The post-simulation results reveal a high precise temporal resolution of 200 ps and a responding range resolution of 3 cm, satisfying the ranging requirements of 3 km laser 3D imaging. Furthermore, the pixel circuit layout area is less than 5095 m2, and the total power consumption is 0.89 mW, having the advantages of small area and low power consumption.