In order to settle the problem of quantitativly estimating ratio of detector noise and analyse whether detecoror noise is the main noise in laser coherent field imaging system,a novel method of quantitative analysis detector noise ratio was proposed.The Signalt-to-Noise (SNR) of the system was given by photoelectron statistics method,and estimating equation of SNR intermediate parameter was derived.A quantitative ratio model of detector noise to total noise was established by SNR equation and estimating equation of SNR intermediate parameter.The ratio model was tested and verified by theory analysis and experiment.The results show that in the specific experiment table,detector noise is about 52% of the total noise.Because the experiment was accomplished at night,turbulence noise and background noise had the least influence on the system,detector noise was the main noise source.The conclusion was acquired that the proposed metod can accurately and effectively estimate detector noise ratio to total noise and has the advantage of simplicity and effectiveness.It can be widely applied in quantitative analysing and measuring of detector noise in laser coherent imaging system.