The invention provides a method for remedying soil heavy metal pollution, improving saline and alkaline land and recycling microalgae for resource utilization through a multi-pond-alga water circulation irrigation system, and belongs to the field of soil remediation and resource utilization. Through the interaction of man-made ponds, microalgae and soil, a pond-microalga combined remediation system is adopted as the core, the soil is prepared and domesticated to remedy the microalgae, the multiple ponds are used for collecting rainwater, the microalgae are cultivated and subjected to expandingpropagation, and the microalgae are sprayed to the field; through circulation irrigation, multi-time spraying and alga water recycling, heavy metal in the polluted soil is taken away, the salinity ofthe soil is reduced, the nutritional ingredients of the soil are improved, and the soil fertility is restored; the microalgae are harvested through the method of pond enrichment and flocculation andaeration, the alga charcoal preparation process is utilized through combination, and resource utilization is achieved; and the system achieves automatic control through a sensor, a PC and a control component. The remediation method comprises a heavy metal/saline and alkaline land remediation microalga cultivation system, a water collection system, an intelligent spray irrigation unit, a microalgarecycling system and a microalga resource utilization system.