A signal model based on Fractional Brownian Motion(FBM) is a common model in nature. Based on the study of the characteristic of signal incremental FBM model, a new method which is different from Iterated Function System(IFS), is proposed to describe the signal. The incremental matrix is a quasi-Toeplitz matrix and the problem is transformed to solve a quasi-Toplitz matrix equation. Experimental results show that this method can approach the signal and make up for the default caused by the method of IFS.