The invention belongs to the technical field of environmental greening, and particularly relates to a green land with an underground conservation pool and a construction method of the green land. The green land comprises a planting layer and the underground conservation pool, wherein the middle of the planting layer is low, the height of two sides of the planting layer is increased gradually, a flat ditch is formed in the lowest position, and an inspection well is arranged in the lowest position of the flat ditch; or the planting layer is high in the periphery and is gradually lowered towards the middle, the inspection well is arranged in the lowest position and provided with a sewer downwards, and the sewer is connected with the underground conservation pool. The underground conservation pool is arranged under the green land and can store rainwater for later irrigation under the drought condition, besides, humidity detectors are arranged in planting grooves in the green land, and a spray pump is automatically opened for watering the green land when the humidity is lower than lower limit, so that manpower and material resources are saved.