The present invention relates to a method for detecting sea fog at daytime and night with polar-orbiting meteorological satellite. The polar-orbiting satellite information is used. The original data file is read into. The medium-high cloud, the clear-air water, the solar flare water, the cloud shadow areas, the sea-ice-snow sheets, non-warm low clouds, warm broken low clouds and wind edges are respectively filtered with a three-stage determining method through comprehensively using the multi-channel optical spectrum information, NDVI index, NDSI index and average month SST in thirty years. The sea fog arrangement areas are obtained and the file comprising sea fog detecting result is generated. Namely the image display can be executed on a microcomputer with GRADS drawing software. The method according to the invention separates the sea fog from low cloud thereby realizing the real-time monitoring of sea fog. Effective meteorological information with real time monitoring is provided for the safe flying over sea surface, marine traffic transportation, seaport and coasting airport operation.