The invention relates to a CT19 mechanism spring disassembling and assembling device. The CT19 mechanism spring disassembling and assembling device comprises a support, wherein the support is formed by a surface plate and side plates. A clamping device, a limiting device and a stretching device are arranged on the support. The clamping device comprises clamping blocks, wherein the clamping blocks are arranged on a guide rod which is located between the side plates. The clamping blocks are lifted and pressed by a first press rod, and combination and separation of the clamping blocks are achieved through linkage between a first connecting rod and a first push rod, so that clamping of a spring is achieved. The limiting device comprises limiting clamping blocks, wherein the limiting clamping blocks are hinged. The limiting clamping blocks are lifted and pressed through a second press rod, and combination and separation of the limiting clamping blocks are achieved through linkage between a second connecting rod and a second push rod, so that limiting of the spring is achieved. By the use of guide grooves formed in the side plates, the stretching device stretches the spring through an insertion part inserted into the spring according to the lever principle of supporting rods, and disassembly of the spring is achieved in the stretching process. The invention further relates to an application method of the CT19 mechanism spring disassembling and assembling device. The CT19 mechanism spring disassembling and assembling device can be rapidly installed and fixed, accomplishes stretching and disassembling operation of the spring at the same time, avoids popup of the spring in the disassembling process, and can also conduct rapid assembly on a spring for replacement.