Abstract: Based on the research of the reputation theory, a reputation rating model based on Dirichlet probability density function and “ad-sensitive” rating rule is proposed in e-commerce. The model takes discrete ratings of entity as input, and derives the continuous measures. “Bad-sensitive” rating rule makes the model sensitive and more cautious to the bad ratings and. The model is self-adaptive as the increasing of ratings. Experiments show that the model has several good characters for the reputation rating in e-commerce.