1. According to the structural characteristics, it can be divided into three types: rack jack, screw (mechanical) jack and hydraulic (hydraulic) jack.　　

① Rack jack: Human power drives the rack to lift heavy objects through levers and gears. The lifting weight generally does not exceed 20 tons, and it can support heavy objects for a long time. It is mainly used in places where operating conditions are inconvenient or where the lower supporting claws need to be used to lift heavy objects, such as railroad lifting operations.　　

② Screw jack: It is driven by manpower through a screw pair, and the screw or nut sleeve is used as the lifting part. Ordinary screw jacks support heavy objects by the self-locking action of the thread, and have a simple structure, but the transmission efficiency is low and the return stroke is slow. The thread of the self-falling screw jack has no self-locking effect, but is equipped with a brake. When the brake is released, the heavy object can descend quickly by itself, shortening the return time, but the structure of this jack is more complicated. Screw jacks can support heavy objects for a long time, with a maximum lifting capacity of 100 tons, which is widely used. After the horizontal screw is installed on the lower part, the heavy objects can be moved laterally in a small distance.　　

③ Hydraulic jack: A hydraulic pump is driven by manpower or electricity, and is driven by a hydraulic system, using cylinders or pistons as lifting parts. Hydraulic jacks can be divided into integral and separate types. The integral pump is integrated with the hydraulic cylinder; the separate pump is separated from the hydraulic cylinder, and the middle is connected with a high-pressure hose. The hydraulic jack has a compact structure and can lift heavy objects steadily, with a lifting capacity of up to 1,000 tons, a stroke of 1 meter, and high transmission efficiency, so it is widely used; but it is easy to leak oil and is not suitable for long-term support of heavy objects. If long-term support needs to use self-locking jacks, screw jacks and hydraulic jacks can be made into multi-stage telescopic types to further reduce the height of the profile or increase the lifting distance.
In addition to the above-mentioned basic types, hydraulic jacks can be converted into sliding form jacks, hydraulic lifting tables, tensioning machines, etc. according to the same principle, for various special construction occasions.

2. According to other methods, it can be classified into separate jacks, horizontal jacks, claw jacks, synchronous jacks, integrated jacks, electric jacks, etc.!　

① The claw jack is a small and light lifting device that uses a rigid lifting piece as a working device to lift heavy objects in a small stroke through the top bracket or the bottom bracket. This jack is used when the general jack cannot match the height of the lifting weight. The rocker can rotate 270 degrees, and the oil will automatically return when the height limit is reached. When using, please use the pipe handle to tighten the hydraulic valve bolts first, and then move the hand pump up and down. The jack can be raised, if you want to put it down, please loosen the hydraulic valve bolts slowly to lower it. The jack has no gravity. It cannot be lowered automatically in the state. The top load is twice the claw load. If the height permits, try to use the upper position.　　

② Horizontal jack: This jack is an indispensable lifting device for all kinds of auto repairs, replacing the original trenches and troughs. It is safe to use and easy to move. Tonnage: 10T, 15T, 20T. Lifting height: 1.2m, 1.6m.