Following the basic laws of the market economy and the objective laws of the operation of the power industry, considering the actual situation of the Guangdong power grid, the southern China (starting from Guangdong) electric spot market is designed. The electric spot market system consists of medium-term and long-term trading based on contract for Difference (CFDs) for hedging risks and centralized spot market for price discovery. Two settlement mechanism based on locational marginal price is applied. The designed spot market system changes the original medium-term and long-term trading based on physical transactions to that based on CFDs, with increased transaction types and transaction frequency, which helps to improve market liquidity. Centralized spot market, including day-ahead and real-time markets, can form a power price signal reflecting the physical operation characteristics of the power system, and promote resource allocation optimization.