The invention discloses a water trap with anti-backflow and water seal that is not easy to dry up, comprising a water trap shell and a water seal structure, the water seal structure includes a water seal outer sleeve, a water seal inner sleeve, an upper floating cover and an upper floating cover, The bottom of the water seal inner sleeve is suspended above the bottom cover, the water seal outer sleeve is installed on the bottom cover, the water seal inner sleeve is inserted into the inner cavity of the water seal outer sleeve, and a vertical waterway and a water channel are formed between the water seal inner sleeve and the outer sleeve The upper port and the lower port, the upper floating cover and the lower floating cover are ring-shaped, which are set on the water seal inner sleeve and can be lifted and lowered along the outer wall of the water seal inner sleeve. port, between the water seal outer sleeve and the water seal inner sleeve and at the corresponding position of the lower port of the vertical water channel, the lower floating cover is built on the supporting structure to unidirectionally seal the lower port of the vertical water channel. A closed vertical water seal is formed between the outer jacket, the water-sealed inner sleeve, the upper floating cover and the lower floating cover, which can effectively prevent odor, cockroaches, backwashing and drying out.