The confidence band model of uncertainty propagation on vector buffer in GIS is proposed in this paper. The buffer confidence band of point feature and liner feature is discussed respectively. A new coefficient

K

similar to relative accuracy is suggested to estimate confidence band quantitatively. The formula to compute the coefficient is introduced. The test section mainly discusses the effect of the factors

finally this paper concludes that the error of line vertex and confidence level is the key factor to the uncertainty propagation during the buffer operation.