The invention relates to a samson post type ocean platform crane base frame comprising a base of a truncated-cone-shaped structure, a rotating table used for being connected with a cantilever crane, a samson post and a portal frame. The samson post is fixed to the base. The rotating table is connected with the lower portion of the portal frame through pin shafts. The samson post is sleeved with the rotating table and the portal frame. A longitudinal-movement-prevention device used for preventing the portal frame from longitudinally moving is installed at the upper end of the samson post. The longitudinal-movement-prevention device comprises an upper supporting pipe vertically fixed to the top of the samson post, and a pin shaft installed on the upper supporting pipe, the pin shaft penetrates a radial pin shaft hole of the upper supporting pipe and is locked on the two sides through bolts, and a bearing assembly used for making the portal frame rotate around the upper supporting pipe is arranged between the pin shaft and the upper end face of the samson post. The samson post type ocean platform crane base frame is simple in structural design, convenient to install and high in maintainability, and improves the use stability, under severe working conditions, of crane metal structures.