Coal is the main energy in China,which has greatly promoted the development of national economy. With the exploitation of high-quality coal,the content of fine coal and the difficulty of coal washing increase gradually. For the problem of low-quality coal (fine coal and slime) with high water content and low calorific value in coal preparation plant,the drying research was conducted by moisture meter,thermogravimetric-gas chromatograph-mass spectrometer instrument. The moisture occurrence characteristics and pyrolysis characteristics were examined,the temperature ranges for moisture removal were studied,and the best condition of low-quality coal drying was revealed. The decomposition temperature of coal was studied,and the pyrolysis process at different stages was revealed. The influence of vibration frequency on the separation effect of 6-0.5 mm coal was investigated by compound dry separator. The results show that for the fine coal and slime,the external water content are 17.84% and 39.20%,and the internal water content are 10.97% and 9.54%,respectively. The external water content of slime is higher than that of fine coal,and the internal water content is similar. The pyrolysis process can be divided into three stages. Water escapes before 101.9 ℃,and the critical temperature for the decomposition of macromolecules in coal is 305.7 ℃. For the 6-0.5 mm coal,when the vibration frequency of compound sparator is 36 Hz,the clean coal yield is 45.48% and the ash content is 10.36%, which effectively realizes the quality improvement and ash reduction of low-quality coal.