The utility model discloses a large negative pressure deep pumping type oil pump and relates to a deep pump. The large negative pressure deep pumping type oil pump is used for solving the problems that the existing oil pump is small in pumping force and incapable of effectively amplifying production pressure difference, and the large-diameter oil pump can not be applied due to limitation of lifting capability of a ground oil pumping machine and is non-ideal in yield-increasing effect and the like. The large negative pressure deep pumping type oil pump comprises a pump barrel and a piston, wherein a diameter changing mechanism is arranged on a barrel body of the pump barrel, the cross sectional area of a channel in the barrel body above the diameter changing mechanism of the pump barrel is smaller than that of the channel in the barrel body below the diameter changing mechanism of the pump barrel, the piston is provided with a shape mechanism matched with the structure of an inner cavity of the diameter changing mechanism, the cross sectional area of the part of the piston, which is positioned above the shape mechanism is smaller than that of the part of the piston, which is positioned below the shape mechanism, a through hole is arranged in the piston, and a valve is arranged in the through hole. The large negative pressure deep pumping type oil pump disclosed by the utility model has the advantages of capability of increasing productivity, simple structure, convenience in use and maintenance and the like, and is mainly used for oil pumping of an oil field.