The development of transportation infrastructure can stimulate economic growth. However, the environmental and human health risks associated with the release of traffic-derived microplastics (MPs) into the ecosystem must also be considered. This study examined four types of soil samples collected from the Qinghai-Tibetan Plateau along the Gemang Highway. The abundance, size, morphology, and types of MPs were analyzed using laser direct infrared (LDIR) spectroscopy to gain a better understanding of their distribution and characteristics. The average abundance of MPs in the study area was 2247.92 f 2053.82 n/kg. It showed the characteristics of wasteland (4726.67 f 2956.76 n/kg) > wolfberry plantation (3294.44 f 2881.93 n/kg) > sandy land (1519.44 f 282.65 n/kg) > soil along the highway (1144.44 f 611.01 n/kg). 67.25% of MPs had a particle size of less than 100 mu m, posing greater environmental risks. The 6 factors identified by the PMF model suggested a variety of potential sources of MPs and highlighted their connections to the transportation sector. The ecological risk assessment of MPs demonstrated a significant degree of risk, with particular concern regarding more toxic plastics use. This study provides fundamental data for the source analysis and ecosystem risk assessment of MPs derived traffic.