In order to solve the problem of particle size information loss in dynamic light scattering inversion by truncated singular value decomposition method, on the base of analyzing the difference of particle size information distribution in autocorrelation function at different delay time, extended truncated singular value decomposition method was proposed which uses nuclear matrix and particle size information distribution in autocorrelation function at different delay time in the same angle to build the extended nuclear matrix. The method adjusts the contribution of the original nucleus matrix datas to the SNR at the same time using the particle size information at each delay time in the autocorrelation function, thereby preserves more effective singular values and reduces information loss due to singular value truncation. On the basis of ensuring noise reduction, the information utilization for the autocorrelation function is improved. At noise level 1×10－3, the datas a set of single peak width distribution (260 nm) and three sets of bimodal particle distributions (250/750 nm), (270/800 nm) and (306/974 nm) simulated in dynamic light scattering in single angle, 3 angles and 6 angles was inverted. The results show that, compared with truncated singular value decomposition method, the peak size errors and distribution errors obtained by extended truncated singular value decomposition method are obviously reduced. The inversion of the measured datas for 306/974 nm particle system in 6-angles shows that the peak particle size error obtained by the extended truncated singular value decomposition method is reduced from 0.032/0.016 by the truncated singular value decomposition method to 0.029/0.006, and peak ratio is closer to actual value.