In this paper, a low temperature Cu—Cu diffusion bonding process is introduced, and an acoustooptic modulator is fabricated by using the electron beam evaporation of Cr/Cu thin film as bonding layer.The experimental results show that the bonding strength of the device can reach 2.7 MPa when the thickness ofthe bonding layer of Cr/Cu/Cu/Cr is 755.5 nm, the bonding temperature is 120 ℃ and the bonding pressure is 30 MPa. The modulator fabricated by this process can withstand a maximum electrical power of 8 W/mm2 and a peak diffraction efficiency of 70% has been obtained. This lays a technological foundation for the development of high power acoustooptic devices.