Abstract: Identity-based searchable encryption scheme with a designated tester(dIBEKS scheme) is studied. The dIBEKS scheme proposed by Tseng et al is analyzed and it shows the scheme is not totally based on identity-based cryptosystem, and the scheme can not satisfy the dIBEKS ciphertext indistinguishability. The definition and security requirements of dIBEKS scheme are firstly presented, and an efficient dIBEKS scheme construction is proposed. After proving the dIBEKS ciphertext indistinguishability is the sufficient condition for thwarting offline keyword guessing attack, the new dIBEKS scheme can satisfy dIBEKS ciphertext indistinguishability, trapdoor indistinguishability and offline keyword guessing resistance under the adaptive chosen message attack in the random oracle model.