Abstract: This paper extracts the features of water demand of tropaeolum, which is controlled by machine vision technology, it builds up the multi-parameter fuzzy judgement model based on the colour values,R ,G,B,r,b, through fuzzy mathematics, which can meet the water need of tropaeolum growth and development, and verifies it by experimental data. These experiments show that this system can judge the condition of water demand tropaeolum for growth development, and calculate the length of time of tropaeolum that is short of water. This system laid a solid foundation for formulating the tropaeolum irrigation tactics.