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 μm 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 50×95 μm2, and the total power consumption is 0.89 mW, having the advantages of small area and low power consumption.