Delamination is one of the most common and dangerous failure modes of composite laminates widely used for engineering components. Two distinguishing delamination mechanisms associated with intrinsic damage and extrinsic fiber bridging within the two delamination zones ahead and behind delamination crack tip respectively for both unidirectional (UD) and multidirectional composite laminates are identified. A new mechanism-based cohesive zone model (MB-CZM) with two constitutive laws related to the two distinctive delamination mechanisms is proposed and validated. The application limitations of the current empirical analysis and modelling methods are clarified and a mechanism-based modification of the fracture toughness calculation method is developed and verified with the MB-CZM and numerical simulation of the experimental results. The advantage of mechanisms-based analysis and modelling methodology over the current empirical or semi-empirical analysis and modeling approaches are highlighted and further applications are discussed. The good agreement of the analysis and simulation results with the experimental results provided the verification and demonstration of the capabilities of the proposed mechanism-based analysis and modelling methods. Therefore, the proposed methods can be extended for investigations of delamination initiation and propagation of composite laminates under complex loading conditions such as cyclic and fatigue loading.