The progress of direct trading in Guangdong prov?ince and the foreign power markets is reviewed in this paper.The ba?sic principle of day?ahead market is proposed.Based on the actual situation of Guangdong power industry, the day?ahead market based on total power competition is designed.The object of transaction,mechanism,execution and settlement aredesigned in details. The simulation of the day ? ahead market is launched based on the actual data of Guangdong power grid. The re?sult of the simulation is then analyzed.