When measuring low degree of metamorphism coal such as brown coal and long flame coal, due to their high moisture and volatile content, if they are placed in a loose state in a 900 ℃ furnace for heating, a large amount of volatile matter will be suddenly released. Opening the crucible cover (producing a loud explosion sound) to remove carbon particles results in high accuracy and poor repeatability. If the sample is pressed into a cake, cut into 3mm small pieces, and then tested, the tight sample can slow down the release rate of volatile matter, effectively preventing coal sample deflagration and splashing, making the measurement results stable and reliable.