The automatic food mixing system must always ensure the requirement of liquid level stability in the food and beverage industry. The quality of the controller directly affects the finished product as well as the performance of the workflow. Due to physical quantity constraints (dynamics) in the nonlinear system, fluid level process control is always subject to interference signals from microcontrollers, sensors, electrical circuits, and cross interaction of the nonlinear system. This paper proposes a backstepping sliding mode controller (BSMC), which is a combined control method between BST and SMC. The BSMC controller is designed based on Lyapunov stability theory, this combination is aimed at stable handling of liquids with unstable composition and ensuring high performance against the disturbances of the real mixing system. In order to prove that the quality of the controller conforms to the requirements of liquid level stability, the backstepping controller was tested on the CE117 module of Tecquipment and compared with other control quality such as PI or fuzzy PI.