As the law foundation of the establishing of right to variation in project, the honesty and credit principle has been discussed in this paper.

The theoretical basis for liability for miss promise is breaching the devoir of the foregoing contract that is based on honesty and credit and can be classified into the liability for fault.

Essential reason can be concluded that companies and peasants are lack of honesty and credit.

Good Faith and Its Maintenance in Harmonious Society;

On the Application of the Principle of Good Faith in the Administrative Contract;

An Economic Analysis on the Principle of Good Faith in Law of Contract;

Culpa in Contrahendo is the responsiblity of compensation for damage that the party should be born to the other for violating the honest credit principle in the course of ordering a contract.

The main ideas are:unifing the contract acts,requlating markets activities concerning contracts,giving full play to the effect of the con tract system,distributing the responsibilities of the people concerned,developing honest credit,renewing the contract system,trying to meet the international standards,protecting lawful creditor s rights,ruling out the contract risks.

This paper further clarifies the important roles the honest credit principle should play in the relations of contracts by expounding the concept and making of contracts,contract fulfilment.

The fair idea of action and the principle of good faith;

This text discusses in detail the relationship of the principle of good faith and justice,lawsuit efficiency,and the conflict of the principle of good faith with strict rule from the jurisprudence.

Good faith doctrine,as a“king clause”,is a most important principle in laws.

This paper analyzes that the post-contract duty is based on the good faith doctrine from its producing basis, legal characters and development, and it has the function of balancing the droit and interests between a person and the social, and the function of pursuiting real justice.