The utility model relates to the field of building construction, in particular to a hall rainwater collecting and underground-draining system. The hall rainwater collecting and underground-draining system comprises a catchwater, a water collecting well and a drain pipe, wherein the catchwater is provided with a rainwater strainer, the water collecting well is provided with a well cover, and the drain pipe connects the catchwater with the water collecting well. The catchwater, the water collecting well and the drain pipe are arranged on a terrace surrounding the hall, the drain pipe is buried under the terrace and is inclined towards the water collecting well, an operating pit used in construction is arranged at the position of the drain pipe and the water collecting well, the drain pipe penetrates the operation pit of the drain pipe, and the water collecting well is arranged in the operation pit of the water collecting well. By means of the operation pit, the drain channel is excavated underground, the square ground is protected as far as possible, construction cost is saved, the problem that rainwater is accumulated on steps of a memorial hall is solved, and collected rainwater can be used for watering lawns.