Abstract: The φ20 mm abnormal connection was detected in the back of the lug and electroformed nickel welding position by laser holography detection when zirconium copper (Zr-Cu) inner wall and electroformed nickel outer wall of the hydraulic body were formed in a rocket engine. Three kinds of specimens were used to verified the origin of the abnormal connection, and the reasons for the abnormal connection of laser holography detection were analyzed by microstructure analysis and micro-hardness test. The results show that the original columnar crystals were changed to coarse equiaxed crystals because of the welding heat conduction between the lug and electroformed nickel, and the micro-hardness of the copper coating decreased with the increase of the penetration depth of the electroformed nickel welding, which made the micro deformation difference between the copper coating near the welding zone and the normal position, and eventually led to the abnormal connection of the laser holography detection.