Abstract: 【Objective】 By setting of a field experiment with two cotton cultivars and four level of irrigating water treatments, the paper aims to study the characteristics of the reflectance and the fluorescence parameter Fv/Fm (PSⅡ maximum photochemical quantum yield) in cotton full-boll stage, and establish the correlation relationship between the chlorophyll fluorescence parameters and the hyperspectral vegetation index in the hope of providing a theory for monitoring the water stresses status over cotton canopy by using hyperspectral remote sensing. 【Method】 The reflectance of cotton canopy was measured by Field Spec Analytical Spectral Device in full-boll stage; At the same time, the leaf FV/Fm of cotton was measured by PAM-2100 chlorophyll fluorescence instrument, and the reflection spectrum data and FV/FM of cotton were processed and analyzed by correlation software, and the correlation regression model was established. 【Result】 The variation trend of cotton canopy reflectance spectra under different water treatment conditions was similar. During the full-boll stage, the Fv/Fm of single leaf of Xinluzao NO. 62 was positively correlated with canopy reflectance with the bands of 350-514 nm, 612-692 nm and 1,945-2,076 nm; but it was negatively correlated with the bands of 708~1,361 nm and 1,621-1,740 nm. The vegetation index NDVI (normalized difference vegetation index) and RVI (ratio vegetation index), were constructed by using sensitive bands, and there was a higher correlation between RVI and Fv/Fm (r_RVI-Fv/Fm=-0.721,5^**, n=20, P<0.01). The equation of estimating Fv/FM and RVI was established and the estimated value of FV/FM was positively correlated with the measured value (r_{restimated Fv/Fm-measured Fv/Fm}=0.723,0^**, n=20, RMSE=1.186 × 10^-2). 【Conclusion】 It showed that based on the correlation between the fluorescence parameter FV/FM and the vegetation index (RVI), the water stress status of cotton in boll stage can be monitored.