Theoretical studies of stereodynamics for reaction LiH（v=0, j=0）＋H → Li＋H2 have been carried out with quasiclassical trajectory method on two potential energy surfaces（PESs） structured as W-PES and P-PES. The main difference of the two PESs is at fixed angle of Li--H--H from 110° to 180°. In this angle range, there is an early- staged energy barrier on the P-PES, but there is no barrier on the W-PES. Some studies have been done to explore the influence of the early-staged energy barrier on this exothermic reaction. Integral cross sections, differential cross sec- tions and product rotational angular momentum of the reaction have been calculated. When Ec〈0.48 eV, the do- minant influence of barrier is to restrain reacting. However, when Ec〉0.48 eV, the dominant influence of barrier is to promote reacting. The angular distribution of the product H2 is extremely forward on both the PESs, because the life- time of most complexes is short. Totally, the lifetime on the P-PES is longer than that on W-PES for the existence of the barrier. With the collision energy increasing, on the both PESs, the distribution of the direction of the product H2 angular momentum changed, and there is a trend that peak at （90°,270°） gets weaker and peak at （90°,90°） gets stronger. The energy barrier weakens the degree of the rotation alignment of the H2.
