The bidding mechanism plays a key role in both the trading fairness of participants in electricity market and the interaction between supply and demand.A bilateral block bidding model based on the pool mode is proposed，which includes both supply and demand，and the trading principles and benefits of various parties are analyzed.With the block bidding theory extended to the demand side，not only are the operating characteristics of generators better reflected，but also the price intent of purchasers and the choice of electricity using mode are embodied.Most important of all，while better protecting the interests of purchasers，this mechanism will bring the shifting load’s advantage of flexible consumption into full play and promote peak clipping.Bilateral block bidding is good for large consumers，various kinds of loads，future consumption pattern，overall benefits of the power system and social benefits.