The current status and development of emission trading are introduced through aspects like reduction target， participants， initial allocation， accounting， etc. Characteristics of carbon credit as a special commodity in carbon trading are induced through its processes of accumulation， circulation and consumption. Inter-relationship among emission trading， physical law of power system and economic performance of power market are discussed. Factors that introduce difficulties in corresponding researches are highlighted， including multi-timescale dynamics， massive uncertainties， multi-player game and cross-discipline interaction. The implementation of experimental economics under the generalized congestion framework are emphasized and suggested for further researches.