With the further reform of the electricity market in China，electricity trading platforms are confronted with more types of market participants，more categories of trading services，and higher trading frequencies.As the core trading intermediary，power trading institutions bear a great number of operating and management costs and face an increasing trading credit risk，namely the risk that market participants may fail to fulfill their contractual obligations on time.The credit risk resides in trading accounts and is closely related to market fluctuations and the financial status of market users.This paper introduces the traditional credit risk measurement model in the international finance field.Based on the electricity market simulation results of a province，the paper utilizes hybrid credit scoring model to quantitatively analyze the default risks that power trading institutions may face in the spot market.The research focuses on the risk of service fee recovery for electricity trading institutions.The simulation results show that default by trading users with exceptionally large trading volumes significantly impacts institutions ’ cost recovery.Under stress test scenarios，such as the simultaneous default of two users with exceptionally large trading volumes，a substantial cost shortfall could arise.Therefore，a more complete protection plan should be formulated to deal with the possible default of large users in the future.