In order to achieve high sensitivity infrared detection ability, the relationship between the charge handling capacity and the detection sensitivity is analyzed, and the pixel-level digital integration technique is introduced. By analyzing noise sources of the whole infrared imaging chains, the signal-to-noise-ratio model based on the pixel-level digital integration technique is established. The design of key parameters and the simulation of noise equivalent temperature difference model are accomplished combining with the application examples. The simulation results demonstrate that the pixel-level digital integration detection technique can break through the constraint that the traditional detection technology only has tens or hundreds of megabytes electron charge capacity, and it can realize the charge handling capability up to kilomega electronic magnitude and high sensitivity up to milli kelvin.