If a contract which includes a payment is null，the rule of Article 157 of the Civil Code of PRC“restitution of property”can be the relief of real right，or the relief of obligation.In particular，when the contract is aimed at the transfer of ownership，and its public notice is not completed，the claim for recovery shall be established，on the contrary，the claim for unjust enrichment shall be established.Recognizing or not the theory of Act of real right does not affect the application of the rules mentioned.Under conditions of nullity，the difference of contract type is decisive to the determination of the claim of restitution.The right of claims derives from property law or unjust enrichment law，or contract law，therefore，the Article 157 cannot be used as the basis of the independent claim.In terms of forms of restitution，the restitution in kind is the principle and restitution in value is the supplement，but the parties may make a special agreement on the form.The Contract Part of Civil Code realizes the renewal and expansion of unjust enrichment law.From the perspective of interpretation，the scope of restitution for the recipient includes the extant enrichments and the fruits，meanwhile，its subjective state should be considered.If malicious，he should return the fruits that should have been collected but not collected.