Abstract
In this paper, the uncertainty theory is used to estimate the vehicle-velocity in accident reconstruction and its uncertainty. Many uncertain factors exist in a road traffic accident. According to these factors, the pre-impact vehicle-velocity can be calculated with some uncertainty. From the factors, a factor is selected as the uncertain-factor having the most uncertain information. Then the uncertain-factor can be used to ascertain an error limit or a value scope of the velocity result. The friction-coefficient and the pre-impact velocity of another vehicle are regarded as the uncertain factors, upon that the method is practiced in the algorithm of kinetic energy and momentum equation.