The present study explores the effects of void-reactivity feedback and neutron interaction on the nonlinear phenomena of a seven-nuclear-coupled boiling channel system with a constant total flow rate. The results show that the void-reactivity feedback and the neutron interaction both have significant effects on the nonlinear characteristics of this system. The complex nonlinear phenomena may depend on the magnitudes of the void-reactivity coefficient and neutron interaction parameter. The results demonstrate that complex nonlinear phenomena, i.e. various complex periodic oscillations and complex chaotic oscillations, can appear in the present system as the variations over certain values of void-reactivity coefficient and neutron interaction parameter under some specific operating states. These imply multiple complex periodic and chaotic attractors, with very interesting and peculiar shapes on the phase space, exist in this system.