Abstract: Multifractal theory is introduced for modeling HF radar sea clutter, and a new time-domain model based on multifractal for HF sea clutter is presented. Simulation analysis indicates that the multifractal model has a similar multifractality with real sea clutter data by comparison among multifractal model, real sea clutter data and Fractional Brownian Motion(FBM) model. In addition, by using probability density function comparison analysis among 3 most commonly used distributions such as Weibull, Log-Normal and Rayleigh distribution, and through a statistical test by modified Kolmogorov-Smirnov(K-S), the conclusion of the proposed multifractal model of HF radar sea clutter possesses the apriori statistical characteristics is obtained, which further proves that this time-domain multifractal model for HF radar sea clutter is quite reasonable and effective.