Properly allocating transmission costs among network users plays a key role in providing appropriate economic signals for planning and siting of generation，transmission and demand sectors，and hence for the secure and economic operation of the whole power system.One of the most important and yet difficult issues associated with transmission cost allocation is the so-called source-sink analysis problem，or in other words，the network use degree evaluation，power flow tracing，power flow separation，or electrical dissection.Up to now，there does not exist a widely accepted approach for making reasonable comparisons among various source-sink analysis methods.Given this background，the problem of how to evaluate various source-sink analysis methods is first addressed.Then，a source-sink analysis method for transmission fixed cost allocation is developed with an objective of maximizing social surplus，in which the generation cost，transmission cost，and customer benefit are all taken into account.Finally，a sample system is served for demonstrating the developed method and for making comparisons among the developed method and several existing methods.