The invention discloses a C-shaped contact channel structure suitable for upper and lower overlapping subway sections and a construction method thereof. One side of the upper overlapping subway section is connected with an upper horizontal channel, one side of the lower overlapping subway section, corresponding to the upper horizontal channel, is connected with a lower horizontal channel, a vertical connecting staircase is arranged between the upper horizontal channel and the lower horizontal channel, a fireproof door with a bidirectional evacuation function is arranged between the upper overlapping subway section and the upper horizontal channel, and a fireproof door with a bidirectional evacuation function is arranged between the lower overlapping subway section and the lower horizontalchannel; a steel supporting and retaining system is erected in the upper overlapping subway section and the lower overlapping subway section, a lower layer subway tunnel deep hole is grouted for reinforcing the stratum, a hole is formed, the lower horizontal channel is excavated to the vertical connecting staircase and is sealed, and the initial supporting is applied in time during the excavationprocess. According to the invention, the structure is reasonable in stress, no land is occupied in construction, the diversion of traffic and change of pipelines are avoided, a large amount of early investment is saved, and meanwhile the vertical steel sleeve method has the advantages of high excavation efficiency and the construction is convenient and safe.