With the development of electricity market mechanism and advanced metering infrastructure (AMI), demand response has become an important alternative solution to improving power system reliability and efficiency. In this paper, the agent-based modelling and simulation method is applied to explore the impact of symmetric market mechanism and demand response on electricity market. The models of market participants are established according to their behaviors. Consumers’ response characteristics under time-of-use (TOU) mechanism are also taken into account. The level of clearing price and market power are analyzed and compared under symmetric and asymmetric market mechanisms. The results indicate that the symmetric mechanism could effectively lower market prices and avoid monopoly. Besides, TOU could apparently flatten the overall demand curve by enabling customers to adjust their load profiles, which also helps to reduce the price.