In order to improve the utilization rate of explosive energy and reduce the amount of welding charge, self-constrained structure explosive was proposed to carry out explosive welding. A T2 copper plate and a Q345 steel plate were used as base layer and flyer layer, respectively, and T2/Q345 explosive welding window was obtained through theoretical calculation. An experimental study on explosive welding of T2 copper and Q345 steel was carried out with double-layer honeycomb structure explosive as self-constrained welding energy. The bonding properties of the clad plate were studied by mechanical property testing and microstructure observation. The results show that compared with single-layer explosive with detonation velocity of 2505 and 3512 m·s^-1, the charge of double-layer honeycomb structure explosive used in T2/Q345 explosive welding can be saved by 54.4% and 31.4%, respectively. The bonding interface of the clad plate transforms from straight to wavy as the propagation distance increases. The tensile shear strength of the clad plate is 237.0 MPa, meeting the requirements of bonding strength of T2/Q345 clad plate. Explosion hardening occurs near the bonding interface. The T2/Q345 clad plate obtained by explosive welding with double-layer honeycomb structure explosive has good bonding property.