Nondestructive moitoring and diagnosis of plant N status is necessary for precision N management. The present study was conducted to determine if canopy reflectance could be used to evaluate leaf N status in rice (oryza sativa L.). Ground-based canopy spectral reflectance and N concentration and accumulation in leaves were measured over the entire rice growing season udner various treatments of N feritlization, irrigation, and plant population. Analyses were made on the relationships of seasonal canopy spectral reflectance, ratio indices, and normalized difference indices to leaf N concentration and N accunulation in rice under different N treatments. The results showed that at each sampling date, leaf N concentration was negatively related to the reflectance at the green band (560nm) while positively related to ration index, with the best correlation at jionting. However, the relationships between leaf N accumulation and reflectance at green band and ration index were consitent across the whole growth periold. The ratio of near infraed (NIR) to green (R480/R560) was especiallly linearly related to total leaf N accrmulation, independent of N level and growth stage. Tests of the linear regression model with different field experiment data set involving diffeent plant densities, N fertilization, and irrigation treatments exhibited good agreement beweent the prediceted and boserved values, with an estimation accuracy of 96.69%, root mean square error of 0.7072, and relative error of -0.0052. These results indicate that ratio inex of NIR to Green (R06/R560) should be useful for nondestructive monitoring of N Status in rice plants.