The invention discloses a small hydropower power purchase model. Generated energy of different time periods of hydropower stations is collected; the hydropower stations are classified and standard samples are selected; correlation coefficients of residual hydropower stations and the standard samples are calculated; which category in the second step the hydropower stations belong to is judged according to the correlation coefficients in the third step; theoretical power purchase peak-to-valley ratios and theoretical power purchase costs of the small hydropower stations are calculated; and actual power purchase costs of various small hydropower stations are calculated and compared with the theoretical costs in the fifth step, thereby judging whether the peak valley power purchase price reduces the power purchase cost of a grid company or not. The model has the advantages that the type of a reservoir is judged and located again through related check in a method, so that the influence of the power purchase peak-to-valley ratios of different types of the hydropower stations on the power purchase cost of the grid company is calculated, a power generation enterprise is guided to reasonably arrange a power generation plan, and the economic benefits of the power generation enterprise are ensured.