This project is about the application of microcontroller in an  aeroponics system. This study focused on improvement for mist propagation system. The purpose of the project is to modify the existing type of control into variable time interval and variable value of mist volume. The existing system apply fixed time interval and fixed value of mist volume for mist propagation system. The disadvantage of this clock-type control is that they must be set for bright sunlight conditions so that the plants do not become dry during periods of maximum stress. In this method, sometimes, the usage of water and energy exceed the required quantity for the plant growth. The technique that has been developed is by using a sensor and manipulates the entire data gained using microcontroller circuit and control the output value of misting volume. A microcontroller circuit controls the duration and time interval of mist propagation system based on the environment relative humidity. An algorithm implemented on the microcontroller make a decision for the best duration and time interval of the mist propagation system. Result of the system testing shows that the microcontroller manage to control the mist propagation system and constant humidity inside the mist chamber area. Further improvement can be made on the controller by implementing intelligent control strategy.