Preparation system and method for formula liquid fertilizer

The invention provides a preparation system and method for a formula liquid fertilizer. The system comprises a flow meter, a raw material tank, an agitator, a liquid level meter, a filter, a metering pump, a mixing barrel, a solenoid valve, a fertilizer filling machine, a check valve and a programmable logic controller; an irrigation pipeline is connected with the raw material tank by the solenoid valve and the flow meter; the raw material tank is connected to the mixing barrel by the solenoid valve, the filter and the metering pump; the mixing barrel is connected to the irrigation pipeline by the fertilizer filling machine and the check valve; the flow meter, the metering pump, the agitator, the flow level meter, the solenoid valve and the fertilizer filling machine are electrically connected to the programmable logic controller respectively. The system has the advantages of automatic operation, labor cost saving, fertilizer saving, improvement of the fertilizer utilization rate, prevention of soil pollution, improvement of the yield and the quality of products and the like.