The invention relates to a method and a device for lap joint friction spot welding of a titanium alloy/an ultra high molecular weight polyethylene. The method for the lap joint friction spot welding of the titanium alloy/the ultra high molecular weight polyethylene includes the following steps that (1) the titanium alloy is enabled to make contact with the ultra high molecular weight polyethylenein a lap-joint mode, and fixed to a worktable by a clamping device; (2) the lap joint contact area is preheated to make ultra high molecular weight polyethylene block materials be softened; and (3) the metal surface is pressed down through a rotary tool, the friction between the rotary tool and the metal surface can generate heat, the rotating speed of the rotary tool is controlled between 500 rpm/min and 4000 rpm/min, the pressing-down speed is between 0.5 mm/min and 6 mm/min, the maximum temperature at the interface position during the connection process is controlled at 230 DEG C-400 DEG C,so that the titanium alloy is connected with the ultra high molecular weight polyethylene. The device consists of the rotary tool, a clamping tool, a worktable main body, a thermocouple and temperature measuring device and a pressure sensor. Compared with the prior art, the method and the device for the lap joint friction spot welding of the titanium alloy/the ultra high molecular weight polyethylene is simple and portable in design, effective and reliable, and can meet the preparation of joints with high strength and connection quality between the titanium alloy and the ultra high molecularweight polyethylene.