After calculating the three companies ' private costs and social costs and comparative analysis of the total environmental cost of the three companies ', we conclude that the initiative way with high private costs but the lowest social costs, the lowest total social cost in the three companies. 通过计算三家企业的私人成本与社会成本之和,比较分析三家企业的环境总成本,得出主动环保的企业私人成本高但社会成本最低,在三家企业中环境总成本最低。