Abstract: The present invention discloses a method and a system for forecasting product sales on a model-free prediction basis, the method comprises establishing a database for storing historical sales data and a variety of variates; providing a preprocessing module for finding major characteristics of sales data from the historical sales data of previous similar products and the corresponding variety of variates thereof stored in the database, and optimizing the major characteristics and coefficients thereof; providing a calculation module for calculating forecast data: substituting covariates to calculate coefficients of a product for forecasting and totalizing the sum of the coefficients of the product for forecasting multiplied by the optimized major characteristics to forecast sales data of the product for forecasting; and providing an output module for outputting the sales data of the product for forecasting.