The pet adoption agreement is equivalent to a civil contract, and it is effective if both parties sign it based on the principle of equality and voluntariness. According to the law, a civil juristic act is valid if it meets the following conditions: (1) the actor has the corresponding capacity for civil conduct; （2） True declaration of intention; （3） It does not violate the mandatory provisions of laws and administrative regulations, and does not violate public order and good customs. However, the contract is invalid in any of the following circumstances: (1) One party entered into the contract by means of fraud or coercion, which harmed the interests of the State; （2） Malicious collusion harms the interests of the state, the collective or a third party; （3） Cover up illegal purpose in legal form; （4） Damage to social and public interests; （5） Violation of mandatory provisions of laws and administrative regulations.
 Legal basis
 Article 470 of the Civil Code of the People's Republic of China [Main contract terms and model text] The contents of a contract shall be agreed by the parties, and generally include the following terms:
 （1） The names and domiciles of the parties;
 （2） Subject matter;
 （3） Quantity;
 （4） Quality;
 （5） Price or remuneration;
 （6） Time limit, place and method of performance;
 （7） Liability for breach of contract;
 （8） Methods of dispute resolution.
 The parties may enter into a contract by reference to model versions of various contracts.