The embodiment of the invention discloses a coke oven combustion exhaust denitration system and a coke oven combustion exhaust method. The system comprises a reduction agent storage device, a reduction agent spraying device and a denitration catalyst layer, wherein the reduction agent spraying device is arranged at the inside of a coke oven heat accumulation chamber; a reduction agent outlet of the reduction agent spraying device is formed in the zone being 850-1100 C DEG C in the coke oven heat accumulation chamber; the reduction agent spraying device is connected with the reduction agent storage device at the outside of the coke oven heat accumulation chamber through a connecting pipeline; the connecting pipeline is provided with a cut-off valve; the denitration catalyst layer is arranged in at least one of the following positions: the zone being 280-800 DEGC in the coke oven heat accumulation chamber, the lower part of a coke over exhaust disk and the inside of a coke oven small flue. Compared with the prior art, the system has the advantages that as the position in which the denitration catalyst layer is arranged is relatively high in temperature, the denitration catalyst layer suitable for relatively high temperature can be adopted; the denitration catalyst is relatively low in price, so that the denitration cost can be reduced.