Mosses, extensively found in boreal forest ecosystems, significantly contribute to the biogeochemical cycling of carbon and nitrogen with these systems. This study focused on two common mosses found in the Da Hinggan Range"s boreal forests, Pleurozium spp. and Sphagnum spp., to evaluate the concentrations and fluxes of dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) in water that percolated through the moss layer during the growing season, spanning from late May to late September. The seasonal variations in dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) within moss throughfall, along with their responses to throughfall intensity and the impacts of various environmental factors, were examined. The findings indicated that the average concentrations of DOC and DON in Pleurozium spp. throughfall were 73.47 and 1.45 mg/L, with average leaching amounts of 3.98 and 0.083 kg/hm2, respectively. For Sphagnum spp. throughfall, the average concentrations were 154.39 and 1.05 mg/L, with corresponding leaching amounts of 12.82 and 0.05 kg/hm2. Due to the high temperature in the middle of the growing season (July and August) and the low rainfall in the end of the growing season (September), the accumulation time of dissolved organic matter is longer, and the nutrient concentrations of rainfall eluting is high. Therefore, the concentrations of DOC and DON in Pleurozium spp.?throughfall in the middle of the growing season (July and August) were significantly (P<0.01) higher than those in the early and the end of the growing season. The concentrations of DOC and DON in Sphagnum spp. throughfall in the early of growing season (May and June) were significantly (P<0.01) lower than those in the middle and the end of growing season. When the throughfall intensity was greater than 0.77 mm/h, DOC and DON leaching amount of Sphagnum spp. increased with the increase of throughfall intensity, and there was a significant (P<0.001) linear correlation between the leaching amount of DOC and DON of Sphagnum spp. and the throughfall intensity. DOC leaching amount of Pleurozium spp. increased with the increase of throughfall intensity, and there was a significant (P<0.05) linear correlation between the leaching amount of DOC of Pleurozium spp. and the throughfall intensity. A highly significant (P<0.01) positive correlation existed between the concentrations of DOC and DON in Pleurozium spp. throughfall and the temperature, and the correlation coefficients reached 0.71 and 0.72, respectively. With the increase of rainfall duration, the rainfall amount becomes larger, resulting in the dilution of nutrient concentration. Therefore, a negative correlation existed between the rainfall duration and the concentration of DOC and DON in the two types of moss throughfall.