A water-circulation irrigation system (10, 10A), comprising: a water supply device comprising a water storage container, an irrigation pipeline, a nozzle and a recycling pipeline, wherein the irrigation pipeline has an end being in communication with the water storage container and another end having a water supply end, and an end of the recycling pipeline is in communication with the water storage container; and a planting device comprising a water collection container, a planting tray and a shunting element, the water collection container having a bottom portion, an external portion opposing the bottom portion, a sidewall and a water dispensing post, the sidewall surrounding the bottom portion in such a manner to form a water collection space and an opening being in communication with an outside, the water dispensing post being disposed in the water collection space to penetrate the bottom portion and the external portion and then extend away from the bottom portion and the external portion, the water dispensing post having therein a water dispensing hole exposed from top and bottom surfaces of the water dispensing post, the planting tray being disposed at the opening of the water collection container, the planting tray having a fitting portion, the fitting portion having therein a through hole and corresponding in position to the water collection space of the water collection container, the shunting element comprising a fertilizer chamber and being disposed at a rim of the through hole of the fitting portion of the planting tray, wherein the nozzle of the water supply device is disposed between a water supply end of the irrigation pipeline and the fitting portion of the planting tray of the planting device, wherein the water dispensing hole of the water collection container of the planting device is in communication with another end of the recycling pipeline of the water supply device and thus in communication with the water storage container. a water supply device comprising a water storage container, an irrigation pipeline, a nozzle and a recycling pipeline, wherein the irrigation pipeline has an end being in communication with the water storage container and another end having a water supply end, and an end of the recycling pipeline is in communication with the water storage container; and a planting device comprising a water collection container, a planting tray and a shunting element, the water collection container having a bottom portion, an external portion opposing the bottom portion, a sidewall and a water dispensing post, the sidewall surrounding the bottom portion in such a manner to form a water collection space and an opening being in communication with an outside, the water dispensing post being disposed in the water collection space to penetrate the bottom portion and the external portion and then extend away from the bottom portion and the external portion, the water dispensing post having therein a water dispensing hole exposed from top and bottom surfaces of the water dispensing post, the planting tray being disposed at the opening of the water collection container, the planting tray having a fitting portion, the fitting portion having therein a through hole and corresponding in position to the water collection space of the water collection container, the shunting element comprising a fertilizer chamber and being disposed at a rim of the through hole of the fitting portion of the planting tray, wherein the nozzle of the water supply device is disposed between a water supply end of the irrigation pipeline and the fitting portion of the planting tray of the planting device, wherein the water dispensing hole of the water collection container of the planting device is in communication with another end of the recycling pipeline of the water supply device and thus in communication with the water storage container.