Ultrasound contrast agent machinery injection device's L shape tee bend is exclusively used in, owing to instruct rotary switch on and including rotating cylinder case, sleeve pipe, first branch pipe, second branch pipe, third branch pipe, be equipped with a case liquid through hole, the 3rd liquid through hole of the 2nd liquid through hole of case and case on the rotating cylinder case, be equipped with a sleeve pipe liquid through hole, the 3rd liquid through hole of the 2nd liquid through hole of sleeve pipe and sleeve pipe on the sleeve pipe, the cover pipe box is established on the rotating cylinder case, on instruct the upper end of rotary switch fixed mounting at the rotating cylinder case, the lower extension section control rotary column that is equipped with downwardly extending of serving of rotating cylinder case, lower the serving of extension section control rotary column is equipped with support rotating switch piece, the bottom of supporting the rotating switch piece is equipped with fixed jack, supporting the rotating switch piece and including first turning block and second turning block, be equipped with the promotion inclined plane on the second turning block, when consequently using, the tee bend wholly can be placed and used on ultrasound contrast agent machinery injection device.