The invention discloses a mountainous city storm radial-vertical flow type denitrification device. The device is composed of an overflow port 1, a planting layer 2, a filtering layer 3, a denitrification layer I4, a denitrification layer II5, a planting vegetable 6, an outfall 7, and a geotechnical cloth 8, wherein the overflow port 1 is 0.5-1.0m higher than the surface layer of the planting layer 2, the thickness of the planting layer 2 is 0.3-0.5m, and the planting layer 2 is composed of a sandy soil mixture in sand and soil volume ratio of 8: 2; the filtering layer 3 is located at the lower part of the geotechnical cloth and composed of river sand; the denitrification layer I4 is located at the lower part of the filtering layer 3, and the height is 1.0m, and the cross section of the denitrification layer I4 is 1/3-1/2 that of the filtering layer 3; the denitrification layer I4 is composed of an outer room 9, a middle room 10 and an inner room 11; the denitrification layer II5 is located at the lower part of the denitrification layer I4, and the inner chamber 11 of the denitrification layer II5 is communicated with the outer chamber 9 of the denitrification layer I4. The denitrification device has the following advantages: (1) the structure is compact, and the floor is saved; (2) the denitrification efficiency is high, and the control effect to the initial rainfall radial flow pollution is good.