Submerged plants play an important role in improving eutrophic water and rebuilding aquatic ecosystem. Using remote sensing technology, the distribution and growth of submerged plants can be monitored in real time and in large area. The depth from the water surface to the plant canopy (WDC) directly affects the accurate remote sensing interpretation of submerged plants in lakes and rivers. Based on the measured spectral data, the spectral characteristics of submerged aquatic vegetation in Lake Ulansuhai were analyzed, and the effects of canopy water depth on the reflectance spectra of submerged plants in Lake Ulansuhai were studied. The retrieval model of canopy water depth of submerged plants in Lake Ulansuhai was established. The results showed that 1) There is a reflection peak near the 1662 nm and 2223 nm of the short wave infrared of the emergent plants, which is an important band that distinguishes the emergent plants from the submerged plants and the floating algae. The spectral reflectance of the submerged plants (WDC=0) and the floating algae is very close, but there are obvious differences in the green band (550-690 nm). Therefore, the spectral characteristics of the green band and the short wave infrared band can be used to distinguish emergent plants, submerged plants and floating algae. 2) The spectral reflectance of submerged plant community decreased with the increase of WDC, and it changed most obviously in the range of 700-900 nm, and there was a significant negative correlation between the spectral reflectance of submerged plant community and WDC near the range of 700-735 nm. 3) A single band / band ratio retrieval model of WDC is established, in which the band ratio retrieval model is better than the single band retrieval model. The R² of the band retrieval model is more than 0.70, the RMSE<13.70 cm, the MRPE<28%, and the retrieval accuracy is high, which is suitable for retrieval of canopy water depth of submerged plants of 10-60 cm. 4) The situ spectral reflectance is integrated into the Landsat-8 OLI band by using the spectral response function, and the retrieval model of the water depth of OLI is established. Among them, the power function model of band ratio has the best retrieval effect, the R² is 0.49, the RMSE is 18.17 cm, the MRPE is 40.05%, which can be used for the retrieval of the water depth of the submerged plant canopy in Lake Ulansuhai after accurate atmospheric correction.