The embodiment of the invention provides a corn leaf equivalent water thickness inversion method and system. The corn leaf equivalent water thickness inversion method comprises the steps: determiningparameters needing to be calibrated in a PROSAIL model according to the sensitivity degree of all the parameters; taking parameters needing to be calibrated as variable parameters to combine with thePROSAIL model, and obtaining a lookup table; calibrating the parameters needing to be calibrated to obtain posterior distribution corresponding to the parameters needing to be calibrated, and constructing a cost function based on the weight difference and the form according to the posterior distribution corresponding to the parameters needing to be calibrated and the actual spectral reflectivity of the corn canopy; and when the minimum value of the cost function is taken, carrying out inversion by utilizing the lookup table to obtain the equivalent water thickness of the corn leaves. Parameters needing to be calibrated and variable parameters of the lookup table are determined by carrying out global sensitivity on the PROSAIL model; the variable parameters of the PROSAIL model are obtained, and calibration and uncertainty analysis are carried out on the variable parameters, thus obtaining the uncertainty of the parameters and the PROSAIL model in the inversion process; and as a variable correction item is added into a cost function, the ill-conditioned problem of inversion is effectively avoided, and the inversion precision is improved.