Experimentation was conducted to analyze the diesel particulate filters (DPF) trap under four different engine loads with particle size analysis and thermo-gravimetric analysis introduced to characterize particulate matter (PM) samples. DPF regeneration was achieved utilizing an oxygen-fed non-thermal plasma (NTP) injection system. Results indicated that accompanying the increase of engine load, the concentration of nucleation mode particles decrease while that of accumulation mode particles and the total concentration number increase at first and then decrease with the total concentration number of PM peaking at 50% load. H2O and soluable organic fraction in PM demonstrate a downward trend while dry soot exhibits an upward trend in mass fraction with the increasing load. NTP may then separate PM into CO and CO2. Size distribution and ingredients of PM trapped by DPF under different loads vary, thus the intensity of reaction between PM and radical gases produced by NTP is different. C-1 (C in CO) exhibited a declining trend with the increasing of engine load, while C-2 (C in CO2) and C-12 (sum of C-1 and C-2) increase first and decrease after. Mass of PM removal maximizes at 50% load while DPF regeneration effect is the most remarkable.