In dealing with the construction contract, to establish a contract is a result of judgment of facts, to be valid is a result of judgment of law and to come into force includes both above two. There is some close relation between subcontracting construction partly and general contracting, contract subcontracting, joint contract, but is different from subcontracting construction wholly in nature. The reasons, causing construction contract to be null and void, are various. In dealing with invalid ones, the clients should be claimed to undertake some responsibilities according to different conditions. These responsibilities involve relevant administrative responsibility in addition to civil responsibility such as reimbursement, compensation at a discount, restitution of damages and taking over the property.