Mowing is one of the main management methods for grasslands. Moderate mowing not only increase grassland productivity, but also maintain high species diversity and stability of the grassland ecosystem. The grassland in agro–pastoral ecotone is subject to multiple interferences from human production and life. How to coordinate grassland production and ecological balance in agro–pastoral ecotone is an urgent problem that needs to be solved. In order to study the effect of mowing on grassland productivity in agro–pastoral ecotone, an experimental platform with different mowing intensity was set up in the typical agro–pastoral ecotone of Youyu county, Shanxi. Mowing intensities were represented by stubble height of 10 cm (LM, Light mowing), 5 cm (MM, Moderate mowing) and 2 cm (HM, Heavy mowing), and enclosed plots were set as the control (CK, No mowing). We used the "harvest method" to collect and monitor the leaves and shoots biomass of dominant species (Leymus secalinus), aboveground biomass, and belowground biomass at different soil depths (0—10 cm, 10—20 cm and 20—30 cm) of plant communities under different mowing intensities. The results showed that: Three years of continuous mowing reduced aboveground biomass of the plant community year by year (P<0.05), while also decreasing underground biomass year by year, but it promoted the accumulation of root biomass on surface of soil (0—10 cm) in drought years. Compared with no mowing, short–term light mowing and moderate mowing significantly reduced aboveground productivity of the community (P<0.05), while heavy mowing had a promotion effect on the biomass of L. secalinus, which is an absolute dominant species in the community. Mowing could promote root growth in 0—20 cm soil layer, but different mowing intensities had no significant effect on belowground productivity of community (P>0.05). Mowing increased the root to shoot ratio of plant communities, which first increased and then decreased with increasing mowing intensity, and reached its maximum value during moderate mowing. In drought years, no or light mowing management should be adopted to alleviate the environmental pressure on grassland. In wet years, heavy mowing management should be adopted to obtain higher aboveground biomass. Thereby achieving coordinated development between grassland production and ecology. Our work has found that short-term mowing management can affect the biomass of dominant species, above- and belowground biomass of grassland plant communities in agro–pastoral ecotone of northern Shanxi. This can provide the scientific basis for livestock production, rational utilization and ecological protection of grassland in agro–pastoral ecotone.