Microplastics are ubiquitous pollutants in aquatic environments. To determine the microplastic pollution status of the Chishui River, the abundance, type, particle size, shape, ecological risk, and potential sources of microplastics were systematically studied using laser direct infrared (LDIR) technology. The results demonstrated that the abundance of microplastics in the surface water of the Chishui River ranged from 9.34 to 69.67 n/L, with an average abundance of 24.87 n/L. The three most abundant types of microplastics were polyethylene terephthalate (PET), polypropylene (PP), and polyamide (PA). The majority of microplastics were ≤50 μm in size, and most particles were fragmented. Pollution can originate from domestic garbage, sewage, and industries. The polymer hazard index (PHI), pollution load index (PLI), and pollution risk index (PRI) methods content of microplastics in the Chishui River Basin indicated a relatively light degree of pollution, and the overall risk level was deemed to be relatively low, with Polyvinylchloride (PVC) plastic being the main risk source. Thus, strengthening the control of plastics such as PVC is recommended to protect the ecological safety of rivers.