Abstract: Microplastics (MPs) are plastic fibers, particles, or films with a particle size of less than 5 mm. They are widely found in water, soil, and atmospheric environments. Because of their small particle size, large surface area, strong adsorptive capacity and other characteristics, they can adsorb heavy metals, persistent organic pollutants, environmental endocrine disruptors and other substances. When humans are exposed to microplastics, they can not only have toxic effects on the contact sites, but also be able to penetrate through tissue barriers and enter other organs, which may cause systemic toxic effects. Existing epidemiological and toxicological studies have shown that microplastics can cause damage to the digestive, respiratory, nervous and reproductive systems. However, their bio-distribution, metabolic characteristics and toxic mechanisms have not been fully clarified. This study provides a systematic review of the absorption, distribution, metabolism and excretion characteristics of microplastics in living organisms, and explores the toxic effects of microplastics and their potential molecular mechanisms on multiple systems of the body (e.g. digestive system and nervous system) and their key organs (e.g. intestines and liver), taking into account the factors such as their size and chemical composition. The aim is to provide a scientific basis for a comprehensive assessment of the health risks of microplastics and theoretical support for the development of relevant prevention and control strategies.