Abstract: The investigation of tobacco brown spot in tobacco fields was conducted at Binxian and Zhaozhou counties, Heilongjiang Province, in 2001-2002.The fit of available data to various growth models was tested by comparing determination coefficient and residual mean-square, the results suggested that the logistic model fitted best. Analyzing the causes of the occurrence of tobacco brown spot, it indicated that the primary disease index, daily mean temperature, relative humidity and rain quantity, and number of rainy days were major factors affecting the disease occurrence and epidemic.A predicting model of infection rate in field was founded with stepwise regression analysis, and the epidemic dynamic of tobacco brown spot in field was also forecasted.