Regarding Lorenz model as the forecast equation，this paper investigates the evolution of the number of particles falling into the predefined dynamic window and the average forecast weight X of the Lorenz system. Then we research preliminarily the predictability of the Lorenz system from another point of views, and the influence of the Gaussian white noises on the Lorenz system. The results show that the evolution of the number reflects the predictability of the Lorenz system to a certain extent. For initial value sets in different areas, there are different predictabilities of the Lorenz system, and we find that there are different influences on the Lorenz system from the Gaussian white noises.