The invention discloses a green certificate transaction market efficiency calculation method and system. The method comprises the steps of obtaining various indexes influencing a green certificate transaction market; Calculating a pre-established index system based on each index to obtain each index value; and Calculating green certificate transaction market efficiency based on the index values. The index system comprises: primary and secondary indexes, wherein each primary index comprises a calculation model determined by adopting a sudden change cardinal number method; Each secondary index comprises a standard value calculation formula. the efficiency of green certificate trading markets in different regions is calculated, various indexes influencing the efficiency of the green certificate trading markets are analyzed, quantitative indexes are introduced, weight determination is not needed, the influence of subjective factors is reduced, and good operability and practicability are achieved.