The nano-injection sensor is a new approach towards high-sensitivity short-wave infrared photon imagers. It resolves the conflict of requiring a large area for high quantum efficiency and small area for high fidelity by using a relatively large micron-scale absorbing volume, and nano-scale sensing elements, which regulates the electron flow and amplifies the signal. The front-end electronics for the Single Photon Imaging nano-injection detector consists of an ROIC with 32 × 32 pixel array with a pixel size of 100μm × 100μm. Each pixel consists of a charge sensitive preamplifier with leakage current compensation circuit, a shaping amplifier, an AC-coupled comparator with a 7bit trimming DAC for offset cancellation, a 10-bit counter for photon counting, and a 10-bit shift register for data readout. The ROIC provides dead-time less, continuous readout with 32 parallel LVDS outputs to achieve full frame readout within 5 μs. Simulation results of the ROIC are presented in this work.