Lithium amidoborane (LiNH2BH3) is known as one of the most prospective hydrogen storage materials. In this paper, the differences between two allotropes (alpha-LiNH2BH3 and beta-LiNH2BH3) of LiNH2BH3 in the dehydrogenation properties was reported for the first time. A series of mixtures of alpha-LiNH2BH3/6-LiNH2BH3 with different mass ratios were prepared by ball milling for different time and the contents of two phases in samples were determined with Rietveld's method. The thermal decomposition behaviors of samples were investigated by DSC. It shows that the initial dehydrogenation temperature of samples decreases with the content of alpha-LiNH2BH3 phase increasing. The initial dehydrogenation temperature of alpha-LiNH2BH3 is about 61 degrees C, which is approximately 15 degrees C lower than that of beta-LiNH2BH3. Dehydrogenation kinetic analysis shows that alpha-LiNH2BH3 has the lower activation energy (157 kJ moll and higher rate (k = 1.422 x 101 min(-1)) than that of beta-LiNH2BH3 (272 kJ mol(-1) and 1.023 x 10(-1) min(-1), respectively). It is suggested that alpha-LiNH2BH3 is more supportive for hydrogen desorption. It gives a critical clue on exploring the dehydrogenation mechanism of lithium amidoborane. Moreover, the significant decrease of desorption temperature will shine a light on on-board hydrogen storage systems. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.