A fishy smell in the leukorrhea after menstruation is usually due to bacterial vaginitis, which is caused by bacterial infection during menstruation, possibly due to local impermeability caused by prolonged use of sanitary napkins or sanitary pads. The main symptom of bacterial vaginitis is increased leucorrhea, pus and a special fishy smell. The main treatment is to apply antibiotics, such as metronidazole and clindamycin, or lactobacillus.