Abstract: The relationship between incidence of rice bacterial blight Xanthomonas campestris and grain loss of single\|cropping rice was analyzed by investigating the incidence level and panicle traits of X.campestris at the same site and date. The results showed that there was no significant difference in panicle length and seed number per ear among different levels of infested plants. However， plant height， filled grain number per panicle， empty flat grain number， filled grain weight， total grain weight per panicle， and 1 000\|seed weigh varied or significantly varied among treatments. The differences between control and 1\|2 level plants were not significant， but the related indicators of 3\|4 level plants were significantly less than those of the control. Filled grain number per panicle， grain weight， total grain weight per panicle and 1 000\|seed weight were decreased by 20.9%-30.8%， 24.3%-36.1%， 20.3%-28.1% and 4.3%-7.6%， respectively， while empty flat grain number per panicle was increased by 132.3%-139.8%. The more serious infested plants， the more significant decrease these parameters. Eleven linear regression equations of disease incidence and grain loss of infested plants at the initial， surge and stable periods of X.campestris were constructed. Such information will be useful in providing basis for forecasting and scientifically controlling X.campestris in the Northwestern Zhejiang.

Key words: single\, cropping rice, rice bacterial blight, incidence of disease, grain loss