Strong physical and/or chemical inter-tube crosslinks play a vital role in carbon nanotube buckypapers and composites. However, both underlying mechanisms and regulation patterns remain poorly understood. Here, we employed the coarse-grained molecular dynamics simulations to investigate the nonlinear large-deformation behavior and the fracture mode of crosslinked buckypapers by considering both intrinsic intra- and inter-tube bond-breaking. A critical crosslink density rho(c) is found to divide the deformation mode of buckypaper into two regimes in uniaxial tension, i.e., the bending-dominated mode at rho < rho(c) and the bending-stretching-bending three-stage one at rho > rho(c). This transition is attributed to the stress concentration and the intrinsic bond-breaking in large tensile deformations. In uniaxial compression, it is always bending-dominated, which is independent of crosslinks and compressive strain. Furthermore, there exists another critical crosslink density controlling the ductile-brittle transition of fracture mode of the strongly-crosslinked buckypaper, which is explained from the viewpoint of the collective hierarchical microstructural evolution. This study provides a profound understanding of crosslink effect on the buckypaper, which is of great significance for the optimization design and further practical applications of the promising material. (C) 2019 Elsevier Ltd. All rights reserved.