This paper studies the nature of the firm.The author thinks that economic systems are made up of three forms,economic organization,non-standard economic organization and discursive trader.Being a form of e-conomic organization,the firm will make people integration of future expectation come true.As for the nature of the firm,firstly,the theory"intermediaries"of Daniel F.Spulber is not different from the theory"Transaction Cost"of Ronald Coase.Secondly,the nature of the firm is the basis of credit of contract.The core of governance mechanism of the firm is incentive mechanism,which brings us more profit.Under the present conditions of abun-dance of labour in our country,if labour get less profit,it is no use designing incentive mechanism.