Three offshore areas including the East China Sea, Java Island in Indonesia, and Tampa Bay in the USA were selected as the survey regions. The effects of hydrological conditions on the abundance of microplastic in the survey marine regions were analyzed using the multiple linear regression analysis in this work. The regression models were constructed with the seawater temperature, salinity, and current velocity as independent variables. The models showed that current velocity was the most important factor that affected the accumulation or diffusion of microplastic. Seawater temperature and salinity also affected microplastic abundance by affecting the movement and density of seawater. It is feasible to establish a regression model of microplastic abundance through hydrological data in offshore areas to analyze and predict the migration and accumulation characteristics of microplastic. The interaction of hydrological factors determined the abundance of marine microplastic.