The dynamic and statistical properties of several hard balls restricted in a box are studied.The collision distribution in configuration space is main object of the research. Numerical simulations indicate that the distribution function is uniform (horizontal line) when the radius of balls is very small. This uniform p art decreases with increasing size of the balls, and a double-peak distribution is found when the radius exceeds a critical value. Brownian motion is simulated by using hard-ball systems. It can be found that the mean square displacement is proportional to the square of time, i.e., the transport process is dominated by ballistic transport, rather than a diffusion behavior.