The invention discloses a grid day-ahead power generation plan optimization method for enhancing a new energy acceptance capability based on a controllable load. The method comprises the following steps of firstly, analyzing different types of controllable loads to obtain a controllable load safety operation constraint; secondly, carrying on a research on a controllable load pricing issue, and creating a controllable load quotation curve, wherein the pricing takes account of the sunk cost and the marginal cost of the controllable load and the time cost of the fund; establishing the deterministic model of the periodic fluctuation and the probability model of stochastic fluctuation of the new energy power generation output, so as to establish a power system day-ahead power generation plan optimization module in consideration of new energy power generation consumption and including the controllable load, and creating a controllable load optimal applied strategy. The method stabilizes thefluctuation amplitude of the power system load curve by rationally adjusting the load curve of the controllable load, improves the peak shaving capability of the system, and further improves the new energy power generation acceptance capability of the power system.