In order to study the production flow and nitrogen and phosphorus migration of forestland in the upstream of water source, the artificial simulated secondary rainfall test method was adopted to select Pinus densiflora forest and barren grassland in the upstream of Tai’an City Huangqian reservoir in the mountain area of south central in Shandong province as the research objects to study the characteristics of surface runoff and subsurface runoff and nitrogen and phosphorus loss. The results indicate that:(1)Under the condition of secondary rainfall, the surface runoff of Pinus densiflora forest is less than that of barren grassland. The subsurface runoff of barren grassland is less than that of Pinus densiflora forest. Soil infiltration of Pinus densiflora forest and barren grassland is proportion to vegetation coverage. The characteristics of surface runoff are small in the early stage, with the progress of rainfall, the runoff of Pinus densiflora forest and barren grassland is increasing and beconing stable, the subsurface runoff is later than the surface runoff, and the runoff is relatively stable.(2)Under the condition of secondary rainfall, the total nitrogen (TN) loss of surface runoff presented a higher output concentration in the initial stage. With the progress of rainfall, the output concentration decreased and gradually tended to be stable. TN loss is proportional to the loss concentration. The loss of TN in surface runoff and subsurface runoff in Pinus densiflora forest is lower than that in barren grassland. The TN loss of surface runoff in Pinus densiflora forest is less than that in barren grassland. The interflow presents a relatively stable state. The TN loss in the interflow of Pinus densiflora forest is less than that in barren grassland.(3)Under the condition of secondary rainfall, the total phosphorus (TP) output concentration of surface runoff in Pinus densiflora forest is positively proportional to the loss. The amount of surface runoff and subsurface runoff TP loss in Pinus densiflora forest is lower than that in barren grassland. The total amount of surface runoff TP loss in Pinus densiflora forest was lower than that in barren grassland, and the total amount of interflow TP loss in Pinus densiflora forest is lower than that in barren grassland.(4)The total loss of TN and TP in Pinus densiflora forest and barren grassland is less than that in the secondary rainfall. The total loss of TN is 1.11 times of the previous rainfall. The total loss of TP was 1.15 times of the previous rainfall. At the same time, the loss of TN and TP in Pinus densiflora forest is less than that in the barren grassland. Therefore, compared with the barren grassland, Pinus densiflora forest has a better role in regulating the loss of nitrogen and phosphorus.