A specific digital output research on short-wave infrared InGaAs linear focal plane array (FPA) was reported. Coupled with a laboratory self-designed short-wave infrared 256×1 InGaAs FPA, a successive approximation register (SAR) analog to digital convertor (ADC) with high resolution, low power consumption and small size was designed and fabricated in 0.18 μm CMOS process. The chip consumes 460 μW at a sampling rate of 235 KS/s with the power supply of 3.3 V. The signal to noise ratio (SNR) of the ADC chip is 66.6 dB. The ADC chip was also tested at different integral time to convert the 256×1 InGaAs FPA signal. The results show that the ADC chip can meet the application requirements of the 256×1 InGaAs FPA.