A three-dimensional urban road system, comprising a straight section, a longitudinal slope section and an intersection, wherein the straight section and the intersection are connected to form a road network; the longitudinal slope section is connected with the straight section and the longitudinal slope section is connected with the intersection to realize a connection between the straight section, the intersection and the ground; the straight section comprises a bottom road, a parking layer and a running layer; two-way, parallel ramps on which cars run up and down are arranged between the centre of the bottom road and the parking layer and between the parking layer and the running layer such that cars in the straight section can switch from the bottom road to the parking layer and stop on the parking layer or switch from the parking layer to the running layer and run thereon; wherein longitudinal slope section comprises a bottom road, a parking layer and a running layer; cars smoothly enter the parking layer of the straight section through the longitudinal slope section; ramps are arranged between the corresponding bottom road and parking layer of the longitudinal slope section; characterized in that the bottom road of the straight section comprises: a left portion including: a 4m wide pedestrian way, a 5m wide bicycle lane, a 2.5m wide bus station or a green belt, an exclusive bus way, a bus-first way and a motor way which are totally 10.5m wide; a middle portion including: a green belt or opposite, parallel ramps on which cars can run up and down and which connect the bottom road to the parking layer, totally 9m wide; and a right portion including: an exclusive bus way, a bus-first way, a motor way which are totally 10.5m wide, a 2.5m wide bus station or a green belt, a 5m wide bicycle lane and a 4m wide pedestrian way; the parking layer are two one-way roads (105, 106) which are separated by the space or the ramps and each of which is 13m wide; the running layer has one one-way road including a 1m wide green belt, a 12m wide car access road and a 3.5m wide upward ramp which connects the bottom road to the parking layer and further to the running layer, and the other one-way road including a 3.5m wide downward ramp descending from the running layer to the parking layer and further to the bottom road, a 12m wide car access road and a 1m wide green belt. characterized in that the bottom road of the straight section comprises: a left portion including: a 4m wide pedestrian way, a 5m wide bicycle lane, a 2.5m wide bus station or a green belt, an exclusive bus way, a bus-first way and a motor way which are totally 10.5m wide; a middle portion including: a green belt or opposite, parallel ramps on which cars can run up and down and which connect the bottom road to the parking layer, totally 9m wide; and a right portion including: an exclusive bus way, a bus-first way, a motor way which are totally 10.5m wide, a 2.5m wide bus station or a green belt, a 5m wide bicycle lane and a 4m wide pedestrian way; the parking layer are two one-way roads (105, 106) which are separated by the space or the ramps and each of which is 13m wide; the running layer has one one-way road including a 1m wide green belt, a 12m wide car access road and a 3.5m wide upward ramp which connects the bottom road to the parking layer and further to the running layer, and the other one-way road including a 3.5m wide downward ramp descending from the running layer to the parking layer and further to the bottom road, a 12m wide car access road and a 1m wide green belt.