The invention provides a remote sensing evaluation method of lake water reserves based on multispectral images. The remote sensing evaluation method includes: according to lake water body spectral response characteristics in different bands of multispectral remote sensing images, extracting water body indexes which reflect lake water surface distribution characteristics; according to the extracted water body indexes, obtaining lake water body boundaries, giving actually-measured lake water level information to the lake water body boundaries, and generating lake equal water level line data sets according to different periods of the lake water body boundaries; according to the lake equal water level line data sets, simulating lake underwater topography; and calculating the lake water reserves in different periods according to the simulated lake underwater topography and actually-measured water level data. According to the remote sensing evaluation method, the lake underwater topography is monitored through utilization of multispectral satellite remote sensing data, the utilized satellite remote sensing data substantially can be obtained for free, and the remote sensing data has the advantages of wide space coverage areas and rapid refreshing speed, so that compared with conventional field actual-measurement methods, the remote sensing evaluation method provided by the embodiment of the invention has the advantages of low monitoring cost, convenient refreshing, and possibility of wide-range popularization and application.