With the help of ReaxFF-MD simulations, the non-isothermal pyrolysis behavior of lignite, especially the effect of heating rate on pyrolysis products, has been investigated in detail. The results demonstrate that increasing the heating rate is very helpful for the production of tar at lower heating rates. By contrast, at relatively high heating rates, further increasing the heating rate has less effect on the distribution of pyrolysis products. Moreover, the evolution tendencies of char and tar at lower heating rates are different from those at the relatively higher heating rates, which exist as remarkable turning points in the high temperature region. This is probably because the reaction time is longer at lower heating rates, and the possibilities of condensation and further decomposition of tar are much greater at high temperatures. Additionally, the relationship between system energy and reaction mechanism was revealed. The results indicate that with the same reaction mechanism, the system energies of non-isothermal pyrolysis are approximately equal and hardly affected by the heating rate. Finally, taking 2 K/ps as an example, the secondary reaction mechanism of tar was further analyzed, and some possible secondary reaction pathways were proposed.