This paper modifies the structural model of Chinese brown coal proposed bythe author earlier this year.The molecular formula of the new model is C

102

H

96

O

26

molecular weight 1736u

carbon content 70.51%

ring number 16

ring condensation index 0.294

carbon aromaticity 0.627

hydrogen aromaticity0.292

methane potential 142m

3

/t.The average ring number of the ring clustersis 2

the average H/C atomic ratio of the side chains and bridges is 2.12

the average carbon number of the functional groups containing -CH

2

- is 1.91.Based on the "evolution path" curve obtained from 147 coal samples and the molecular formulas of thermo-degradation products

the author discussesthe thermo-degradation steps of humic coal.