To fully access and compare the condition of power sale markets from perspectives of time and space， this paper presents the new notion of“quality of power sale market” and the associate assessment method. Borrowing ideas from“quality of economic growth” and combining features of power sale markets， this paper discusses the connotation of market quality， and establishes a set of assessment indices. These include aspects of current status， developing speed， stability， benefit and market structure. Moreover， this paper develops a graphical assessing method， which is improved from“radar chart”， to present a quantitative and intuitive assessing result. The study helps the marketing people be well acquainted with the characters of the market they serve， and provides valuable reference for improving the market quality.