The invention relates to a plug of a working cylinder of a hydraulic device and the working cylinder of the hydraulic device. The plug of the working cylinder of the hydraulic device comprises a central hole, the central hole is used for allowing a buffer shaft on a piston of the working cylinder of the hydraulic device to be inserted into, the plug is further provided with a stopping end surfacefor plugging an oil passing hole in a buffer sleeve during being combined with the buffer sleeve, a groove is formed in the stopping end surface, the groove communicates with the central hole, or a communicating channel is arranged on the plug, an opening in one end of the communicating channel is formed in the stopping end surface, and an opening in the other end is formed in the corresponding wall surface of the plug so as to communicate with the working cylinder of the hydraulic device. During starting of the working cylinder of the hydraulic device, the oil liquid in the groove or in the position, located in the opening of the stopping end surface of the communicating channel plays a promotion role in the end surface, close to the working cylinder of the hydraulic device, of the buffersleeve, the promotion force of the oil liquid on the buffer sleeve is increased, and the starting force of the working cylinder of the hydraulic device is increased.