The Earth can be described as having entered a new human-dominated geological epoch that is known as the "Anthropocene", and determining the timing of the start of the Anthropocene has become important. Here, we combined sedimentological parameters (sedimentation rate and mean grain size), geochemical indicators (heavy metal enrichment factors, black carbon fluxes and polycyclic aromatic hydrocarbons concentrations) and a biological indicator (plant macrofossils) in wetland sediment records to assess the start of the Anthropocene. The analysis of five wetlands on the Sanjiang Plain, Northeast China, showed that the major component scores of sedimentological parameters and geochemical features based on principal component analyses had obvious increasing trends after the 1950s. Structural change tests were applied to the plant macrofossil data of one typical peatland to detect the breakpoint of the wetland ecosystem, and the dominant species of the plant community changed from Carex lasiocarpa to Salix myrtilloides during this period due to intensive human activities and drainage in this region. We can divide the history of anthropogenic activities into five periods among the three phases of exploitations that occurred in the Sanjiang Plain, Northeast China, based on our results and historical document records; the anthropogenic activities increased significantly starting in the New China period. It is suggested that the 1950s can be treated as the start of the Anthropocene on the Sanjiang Plain, Northeast China. Similar studies of stratigraphic indicators that provide estimates of historical human activities in other regions could contribute to the global definition of the Anthropocene.