Tests of longitudinal shear capacity of seven lightweight aggregate concrete composite slabs with profiled steel sheet are conducted to study influence factors and computing methods of longitudinal shear capacity of the composite slabs. The results show that shear capacity is higher for the thicker composite slabs and the smaller shear span and transverse shear reinforcements in the composite slabs. Moreover, parameters for the m-kmethod and the partial shear connection (PSC) method are determined for predicting the longitudinal shear capacity of the composite slabs based on test results, in which the shearing bond coefficients m and k gained from this study are more suitable for predicting the longitudinal shear capacity of the composite slabs than ones from other documents, and the longitudinal shear bond strength is linearly associated with shear-span ratio. The results provided by these two methods have a good agreement with those obtained from tests, and provide references for the design of lightweight aggregate concrete composite slabs.