The invention discloses an intelligent preparation method of a liquid slowly-controlled-release fertilizer. A sensing module senses whether adding weights of raw materials reach preset values or not. A temperature detection module detects the temperature in a fourth stirring apparatus. A ventilation detection module detects the ventilation degree in the fourth stirring apparatus. A pH detection module detects the pH value of a solution. A PLC, according to the sensed values, the temperature value, the ventilation degree and the pH value, controls an electromagnetic valve, a grinding module, a stirring module, a sugar / water proportion module, an air blowing module, a temperature control module, the ventilation detection module, a reminding module, a heating module, a material module, a refrigerating module, a drying module, a crushing module, a filter module, a vibration module, a concentration module and a cooling module to execute related operations through internal analysis and calculation. By accurate control on various parameters, the intelligent preparation method effectively improves stability of a slow-release microelement chelating agent and a slow-release micro-crystallized metal salt mineral powder, so that the method is high in production efficiency, satisfies production demand, reduces labor intensity and provides accurate and reliable detection.