The invention aims to provide a pile foundation and vertical shaft integrated semi-direct-drive type tidal current power generation device. An inner cylinder shaft is installed outside a pile foundation in a sleeving mode. An outer cylinder shaft is installed outside the inner cylinder shaft in a sleeving mode and matched with the inner cylinder shaft through a bearing. Wheel hubs are fixed to the exterior of the outer cylinder shaft and connected with blades. The upper end of the outer cylinder shaft is connected with a planet carrier, and planet wheels are installed on the planet carrier. A center wheel is located in the middle of all the planet wheels and meshed with all the planet wheels. The center wheel is installed outside a rotor shaft in a sleeving mode and fixed to the rotor shaft. An outer stator and an inner gear ring are fixed to the inner wall of a case body. The exterior of the rotor shaft is sleeved with an inner rotor matched with an outer stator. All the planet wheels are all meshed with the inner gear ring. The case body is fixed to an inner sleeve. The pile foundation and vertical shaft integrated semi-direct-drive type tidal current power generation device integrates a speed-up mechanism and a permanent-magnet direct-drive type generator, so that an integrated semi-direct-drive type generator case is formed; in this way, the size of a unit is reduced on the basis of meeting the basic requirements for speed regulation of the unit, so that the structure of the unit is compact.