In this work, a phased-array (PA) electromagnetic acoustic transducer (EMAT) is proposed for detection of delamination defect in multilayer tubes of small inner diameter. In order to generate focused ultrasonic waves for the small tube and small defects, a solenoid EM magnet setting outside the tube is adopted for the bias magnetic field generation and an array of bobbin coils setting inside the tube is used to induce eddy current and Lorentz force. Numerical simulations are performed to investigate the validity of the proposed PA EMAT method for monoblock of Tokamak divertor structures. The numerical results show that the detectability can be significantly improved, which demonstrated the validity of the proposed PA EMAT for multilayer tube of small diameter.