There are four important qualifications when the contract for the benefit of third party comes into being.First,basal contract must form availably.Second,promisee and promisor must have intention to benefit the third party.Third,the third party must acquire rights from promisee and promisor directly.Forth,the third party must be specified.Parties of contract can not change nor cancel articles benefiting third party optionally.However,they can agree to cancel contract for the benefit of third party when the third party agrees.On legal conditions of canceling contract,they can cancel without third party's agreement.