The invention discloses a double-speed oil cylinder, mainly comprising a cylinder body, an oil cylinder front cover, an oil cylinder back cover, a large piston and a movable piston rod, wherein the other end of the cylinder body and the movable piston rod form a sealed space by the oil cylinder front cover, the large piston is arranged at one end of the movable piston rod, the movable piston rod is of a hollow structure, a fixed piston rod is arranged in the movable piston rod, the fixed piston rod is of a hollow structure, two ends of the fixed piston rod are communicated, one end of the fixed piston rod is connected with the oil cylinder back cover, one end of the movable piston rod in the cylinder body is sealed with the outer wall of the fixed piston rod by the large piston, and the large piston is glidingly connected onto the fixed piston rod. In the double-speed oil cylinder, a pushing force can be changed by means of the different compression areas of the movable piston rod and the large piston, synchronously the pushing speed and the retreating speed of the oil cylinder can be improved when the smaller compression area is used; therefore, the wood splitting speed can be greatly improved and the working efficiency is improved. A sequence adjusting valve is arranged so that the switching between the fast push and the large pushing force can be automatically realized aiming at requirements on the pushing force; and therefore, the operation is more simple and convenient.