Abstract: A kind of real-time control irrigating system is put forward with fuzzy technology based on the characteristics of the water demand for young plant in greenhouse. And some reasonable fuzzy rules are found by computer simulation in MATLAB. Then, a hardware circuit that Programmable Logic Controller(PLC) is the control center was made, and these fuzzy rules were written in the ladder language. The hardware system was applied in real-time irrigating system for young plant in greenhouse. The debugging results show that it can meet the demands for young plant growing in greenhouse.