This paper introduces a digital readout integrated circuit (DROIC) for 320×256 target-tracking infrared focal plane arrays(IRFPAs). The circuit is based on a two-stage ADC, which implements 10-bit coarse quantization and 4-bit fine quantization, enabling high frame frequency trace detection. In addition, the locating and independent output of sensitive pixels are realized by a scanning function, which greatly reduces output frequency and power consumption. The proposed ROIC of 15μm pixel-pitch is fabricated using 55nm 1P6M CMOS process. The pixel circuit consumes 379nW. Frame frequency of the target-tracking mode is 1 kHz, the two-stage ADC has a nonlinearity of 0.06%.