Abstract: The CYJ type sampling device is installed in the middle of the belt conveyor at a power plant. Because of the unreasonable process control and structure design of the device, the coal samples are not representative. Some improvements on the mechanical and electrical equipment as well as the system protection of the device are made. After such modifications, the technical benchmark, design characteristics and performance testing indices of the device all meet the related national standard and industrial standard. Being capable of sampling mechanically and normatively, it can also provide the reference for the manufacturers and the users.