As an emerging pollutant，microplastics have been received extensive attention all over the world in recent years. However，most of previous research focused on the fate of microplastics in aquatic ecosystems，little has been conducted on the environmental behavior of microplastics in terrestrial ecosystems，especially，study on its toxic effects to crops was rarely reported. A pot experiment was conducted to compare the growth and physiological status of soybean exposed to polyethylene microplastics with different particle sizes(500，1000 μm)and different adding concentrations(1%，5%)and the toxic effect of microplastics on soybean was explored. The results showed that the soybean germination rate under microplastics exposure was reduced by 7.69%～64.91%，compared with the control in two crops planting. The effect of large-grained microplastics(1000 μm)on the germination rate of soybean was more significant，and the inhibitory effect on seedling germination rate was enhanced with the increase of additive concentration. However，the microplastics with small-grained particles(500 μm)showed stronger inhibition on plant height and fresh weigh of soybean，while it had no significant effect on soybean of content leaf chlorophyll. All of these results indicated that microplastics had some negative effects on soybean growth. At the same time，the addition of microplastics obviously inhibited the protein synthesis of soybean over ground，and 500 μm microplastics had a greater effect on the soluble protein content of soybean，which was more than 50% lower than that of the control treatment. Microplastics had a positive effect on the content of cellulose in soybean. Microplastics also affected nutrient uptake and accumulation in the soybean. In two crops planting，microplastics inhibited nitrogen uptake and accumulation in soybean(inhibition rate was 2.75%～29.55%)，while promoted the absorption and accumulation of phosphorus in soybean with the promoting effect being enhanced with the increase of additive amount and particle size. The absorption and accumulation of potassium in soybean were firstly promoted and then inhibited by microplastics in two crops planting. These results will provide profound reference for a comprehensive understanding of the potential biological toxic effects and ecological risks of microplastics in agricultural ecosystems.