The invention relates to an automobile anti-theft and engine anti-water-soaking protection device with improved anti-theft system function, in particular to an automobile anti-theft and engine water soaking prevention protector which is composed of an inlet and outlet connecting pipe (101), a connecting flange (102), a shell (103), a silica gel sealing ring (105), a gland (110), a rotary valve mechanism body (201), a telescopic valve shifting fork (202), a normally open telescopic valve (203), a normally closed telescopic valve (204), a telescopic valve shifting fork dovetail sliding block (206), an intermediate gear (302), a driven gear (303), a 90-degree rotating disc limiting disc (304), a 90-degree rotating disc shifting fork (305), a 90-degree rotating disc (306) and a stepping motor(312). On the premise that the pipe diameter of an air inlet system and the pipe diameter of an air outlet system of an automobile are not changed, and the original structure of the automobile is notchanged, engine damage and scrapping, caused by water invasion, of the automobile are avoided, the maintenance cost for water-soaked vehicles is greatly reduced, and the anti-theft function of automobiles is improved and enhanced.