Market forces evaluation is an important way to provide power market monitoring. Based on own energy structure, Qinghai Province proposes to build a market with total clean energy supply, so it is necessary to find an effective assessment method to reveal the market forces issues under this circumstance. The article introduces the power structure and construction of Qinghai power market, analyzes potential market forces issues and introduces a market forces evaluation index system for spot market with considering characteristics of clean energy. Besides, it comprehensively evaluates the market structure and major producers' degree of monopoly in different space and time scales, and lays the foundation for improvement of Qinghai power market regulation and supervision mechanism.