The invention relates to a method for optimizing steam huff-puff injection parameters based on an approximation model. The method comprises the steps that (1) a steam huff-puff three-dimensional numerical reservoir simulation model is established; (2) four injection parameters including steam injection dryness, a steam injection temperature, a steam injection speed and a cyclic steam injection amount are selected as designed optimization variables; (3) initial value scopes are selected for the injection parameters; (4) an experimental design method is used to select sample points aiming at the steam huff-puff injection parameters; (5) the steam huff-puff three-dimensional numerical reservoir simulation model is used to conduct numerical simulation computation of the sample points; (6) target functions are selected, and the injection parameters of each sample point and corresponding target function response values are used to establish the approximation model which represents the steam huff-puff injection parameters; (7) accuracy of the approximation model is verified, the step (8) will be conducted if accuracy requirements are satisfied, and the step (3) will be restarted if the accuracy requirements cannot be satisfied; and (8) global optimization is conducted to the injection parameters through a genetic algorithm, so that the optimal steam huff-puff injection parameters can be obtained.