Abstract: A water and fertilizer regulation system based on STM32 microcontroller was designed.The system realized regulation of water and fertilizer ratio of different elements by controlling opening of different solenoid valves.Taking lettuce as an example，relationship between different potassium fertilizer concentration and leaf area and plant height of lettuce was studied by adjusting solenoid valve opening of potassium fertilizer concentration under condition that ratio of water and fertilizer of other elements was normal concentration，in order to get solenoid valve opening adjustment strategy，and achieve accurate regulation of water and fertilizer ratio.