The invention relates to a device for adding and hanging well slots for a marine platform, which comprises a well mouth piece frame, guide cylinders, a fixed wedge block and a pipe clamp, wherein 1-6guide cylinders are arranged on the well mouth piece frame, a water partition sleeve pipe is fixed on the guide cylinders by the fixed wedge block, and the well mouth piece frame is fastened on the prior marine oil-gas production platform by the hydraulic pipe clamp. The invention can realize the increase of the number of the well slots of the prior platform so as to meet the production requirement of drilling an adjustment well and also has the characteristics of development cost saving of oil fields, simple structure, short construction and installation period, extensive applicability and the like.