Abstract: The micromechanism is determined by ESEM and the adsorption film thickness is determined by elliptical polarization, which the smooth surface of coal adsorbs the lignosulphonate and modified lignosulphonate. It is disclosed that the intrinsic reason why the pulping property of modified lignosulphonate is better than lignosulphonate. It is researched that the global structure of modified lignosulphonate is dispersive and less cluster structure to benefit the adsorption efficiency, the adsorption capacity and to improve the lyophobic surface of coal;. the film thickness is double by the comparison of lignosulphonate and modified lignosulphonate in the respect of the space steric hindrance.