A transmission parking system is provided. The system includes a parking gear and a parking rod that is connected with the parking gear. Additionally, a parking lever has a first end that is connected with the parking rod and the parking lever is installed rotatably around a control shaft. A detent return spring is wound around an exterior circumference of the control shaft, supports the parking lever, and provides elastic force to rotate the parking lever and return to an original position. A control lever is installed rotatably around the control shaft and is installed at an exterior side of the parking lever to allow user operation. A neutral state maintaining lock and release device is connected with the control lever and is changed to a neutral state lock or a neutral state release based on operation of the control lever.