The invention discloses a water quality evaluation method for improving a Nemerow index based on principal component analysis, and relates to the field of water quality evaluation methods. The methodcomprises the following steps of selecting water quality national standards, and concluding evaluation indexes; completing water quality index data standardization; building a variable correlation coefficient matrix; performing principle component analysis and determining correction indexes; calculating a Nemerow index, and performing water quality evaluation. On the basis of the principle component analysis theory, by means of the dimension reduction characteristic, less index information is used for representing the majority, on the basis of the Nemerow index, by combining advantages of twoevaluation methods, the obtained evaluation result is reasonable and reliable, and the water quality condition can be more scientifically reflected.