The crushed shale ceramist was used to prepare LC60 high strength lightweight aggregate concrete(HLWAC) specimens containing various types of fibers and different fiber volume fractions. Their mechanical properties were studied and the fiber reinforcement mechanism was clarified from microscopic viewpoint. The experimental results show that bonding characteristic between aggregates and cement paste of HLWAC is much superior to that of normal weight concrete. The splitting tensile strength and flexural strength are enhanced while no obvious effect on compressive strength is found. The reinforcement of fibers in HLWAC can be attributed to its bridging mechanism which can impede the development of cracks. Furthermore, the improvement provided by carbon fibers proves to be better than that provided by steel fibers.