The invention discloses a rainwater collecting and reusing system for farm irrigation, and belongs to the technical field of farm irrigation. The rainwater collecting and reusing system for farm irrigation comprises a drainage ditch and a reservoir. The reservoir is arranged at one end of the drainage ditch, a collecting tank is arranged at the other end of the drainage ditch, pebble filter blocksare arranged in the collecting tank and used for filtering water flowing into the collecting tank from the drainage ditch, the drainage ditch further communicates with lamp wick tubes, lamp wick water-absorbent cotton is arranged in the lamp wick tubes, the lamp wick tubes further communicate with a return pipeline, the tail end of the return pipeline communicates with a storage pond, redundant water in the drainage ditch can be absorbed and stored through the lamp wick water-absorbent cotton in the lamp wick tubes, and under the condition of water shortage, the water in the storage pond canbe conveyed to the drainage ditch. The water consumption is greatly reduced, energy saving and environmental protection are facilitated, direct utilization of nitrogen and phosphorus without energy consumption is achieved, settling cells are further arranged at the bottom of the storage pond, silt blockage can be avoided through the settling cells during actual use, meanwhile, straw can be added,replacement use can be achieved, and microorganisms can be degraded.