Signal noise ratio and dynamic range are two very important figures of merit of infrared focal plane readout integrated circuit (ROIC).It is directly relative to temporal noise of ROIC.In this paper,we deeply analyze and study the temporal noise of ROIC,at the same time we give the theory of computing noise method of all kinds of noise sources and the whole ROIC noise.At last,we give the relations between the whole noise,SNR,DR and several circuit parameters.