Splitting brain fissure is an important operative procedure in neurosurgeries. Arachnoid membrane that covers brain parenchyma is generally opened with sharp dissection using microscissors, while connective tissues such as arachnoid trabeculae are fractured by blunt dissection to split a brain fissure. However, most earlier studies about neurosurgery simulation have not given enough detailed model of connective tissues because consideration of connective tissues in simulation requires high computational cost. The objective of this paper is to conduct a brain fissure splitting simulation considering damage of connective tissues. Assuming that connective tissues are homogeneously distributed in a brain fissure, a damage model of connective tissue is proposed. To verify the splitting brain fissure simulation, longitudinal fissure splitting experiments were performed by using porcine brains with different splitting velocities. By comparing the experimental data and the simulation results, simulations can reproduce the reaction force of the brain fissure splitting with connective tissues.