Abstract: The East Mongolia Shengli lignite,with the properties of high porosity,abundant oxygen functional groups on the surface,difficult storage and transportation and poor slurry properties,was modified with the anionic paraffin emulsion,and the change of the surface properties and the pulp properties of the modified lignite were studied. The thermo-gravimetric characteristics of the air dried lignite( ADL) and the modified air dried basis( BADL) of lignite was studied by thermo gravimetric analysis( TG). The change of surface functional groups,specific surface area and pore structure of dry basis lignite dried by hot wind and modified dry basis lignite were studied by X-ray photoelectron spectroscopy and nitrogen adsorption specific surface area test. The pulping property of lignite before and after modification was studied by slurry forming test. The results show that after the ADL modified by the anionic paraffin emulsion,the absolute mass change rate of BADL is less than that of ADL at the temperature range from 50 to 150 degrees centigrade. When the temperature is 117. 82 degrees,the absolute value difference is the maximum 0. 34%/min. When the DL is modified by anionic paraffin milk,the content of the surface inorganic oxygen is reduced from 0. 64% to 0. 20%,and the content of CO and COO— decrease from 13. 93% and12. 22% to 13. 11% and 12. 03%,respectively. The specific surface area changes from 8. 790 m2/g to 14. 995 m2/g; the pore volume decreases from 0. 041 cm3/g to 0. 032 cm3/g,and the average pore size decreases from 32. 697 nm to 17. 054 nm. The coal water slurry viscosity is less than 1 300 m Pa·s,and the liquidity is better than B-( 12 cm) as the standard,the modified lignite is pulped with fractal gradation process,and the maximum pulp concentration can reach 60. 59%. Compared with the single stick grinding process before the unmodified coal,the maximum slurry concentration increases by 10 percentage points,The apparent viscosity decreases from 1 059 to682 m Pa·s,which improves the stability of coal slurry.