Abstract: Longitudinal transverse shear strength is one of the most important factors in evaluating the intensity of composite laminates, while S2/430LV is a typical composite material widely used in warships. This paper first investigates the intensity of ±45° ply in respect with longitudinal shear strength by referring to GB/T3355-2005. The results show that under tension-shear loads, the curves of load/displacement of S2/430LV display two stages as well as arc transition region characteristics. The paper then takes the tangential point between the linear stages and the arc segment in the primary stage of the curves as the datum point of sheared intensity (symbolized by τ_B), calculating the reduction coefficients to investigate tension-shear fatigue, left stiffness, and shear strength. It is suggested that 0.75 should be taken as the reduction coefficient of longitudinal shear strength for S2/430LV composite material,when allowing for reasonable mechanical fatigue. The conclusion has important reference significance for composite materials of warships in terms of reliability design and analysis.