In order to detect obscure targets by the use of LAser Detection and Ranging (LADAR), we constructed the LADAR echo model of obscure targets and obtained the simulation data of LADAR echo of obscure targets. Levenberg-Marguardt method was used to fit the echo waveforms, which decomposed the waveforms into series of Gaussian components, and obtained the number and the position of the Gaussian components, half-width and amplitude of each Gaussian component. Echo components of sub-target in different channels were obtained by time matching of separated sub-echoes respectively, and the characteristics extraction of various targets has been implemented. Classifying the echo characteristics by using K-means helps to classify various echo components. An anticipated result of simulation is obtained by using this method.