Abstract: Abstract: The biomass fuel is defined as burning biomass materials as fuel, which has the characteristics of wide distribution, reproducible and pollution-free. This fuel has become so important in the field of energy resources that the corresponding research has attracted extensive attention from both academia and industry. In order to improve technology of this fuel the physical and chemical properties of internal lignin during the dense forming process of Salix psammophila and its effect on fuel formation was researched in this paper, and a detailed discussion about its bonding mechanism of dense forming was presented. The main research process of this paper could be summarized as: Firstly, by using amporphous cell and forcite related blocks of software Materials Studio 2017, the lignin molecular fragments with different water content were created ( the lignin molecular chain was 10), in the procedure of creation, the initial temperature was 298 K, the pressure was standard atmospheric pressure, and the number of configuration was 2; Furthermore, in conditions of different moisture contents, pressures and temperatures, the molecular dynamics simulation calculation and related property prediction of lignin molecular fragment were conducted, and the diffusion ability of lignin molecules could be investigated by the distribution function in research of the latter, though analysis and calculation, the intervals of lignin molecule strong peak were determined; At last, for guaranteeing the rationality and reliability of bonding mechanism, and better observing the binding mode between particles, the hot pressing forming test of Salix biomass fuel was carried out with reference to the simulation conditions and the obtained results, the characteristics and microscopic morphology of the formed fuel were analyzed with the tested sample. The simulations and test illustrate that: in moisture content of 8%, 11%, 14%, 17%, the glass transition temperature (Tg) of Salix lignin successively were 410, 392, 381 and 376 K. Although the diffusion ability of lignin molecules increased with the increasing temperature, increased first and then decreased with the increase of pressure and water content, and under the case of the pressure was 40 MPa and the water content was 14%, the diffusion ability reached the maximum value. When the water content, the pressure and the temperature were 14%, 40 MPa and 380 K, respectively, water molecules and lignin molecules could form hydrogen bonds, and the main source was predicted to be the interaction between water molecules and cyclic or acyclic hydroxyl groups. Based on the above analysis, the relevant characteristics of the molding fuel was studied, and the result showed that: Firstly, the prediction of properties was more accurate, such as salix lignin Tg; Secondly, though proper moisture and temperature could reduce the molding power consumption and relaxation ratio, the both were not suitable excess high; Thirdly, in vertical direction, under the action of viscous fluid, the fuel interior particles were solidified together superimposed by the method of viscous fluid; Fourthly, in horizontal direction, the main binding modes of fuel interior particles were tiling, lapping and fitting, and had a significant mesh-like structure and this structure related to the rich fibers contained in the sand willow wood, and could effectively enhance the mechanism strength of the particles.