The invention provides a plastic greenhouse extraction method and coverage inversion method based on a medium-resolution remote sensing image. The plastic greenhouse coverage inversion method mainly comprises the following steps that: 1) performing remote sensing image atmospheric correction to obtain the real reflectivity of a ground surface; 2) performing normalized difference vegetation index (NDVI) and normalized difference building index (NDBI) threshold processing to remove dense vegetation and most of artificial ground surfaces; 3) performing plastic greenhouse index (PGI) processing to extract a PG area; and 4) performing PG coverage estimation to predict PG coverage within pixels ( the proportion of the PG in the image pixels). With the methods of the invention adopted, PG area coverage detection can be performed through effectively using the medium-resolution remote sensing image, the PG coverage in the pixels can be effectively estimated, and the accuracy of the monitoring of the PG coverage can be greatly improved.