In this research, we studied the light emission characteristics of GaAs/GaAsSb type II heterostructures in a photonic nanocavity. In a type II heterostructure, because of the spatial separation of electrons and holes, light emission efficiency is typically very small. However, by coupling the emission peak with the cavity mode, we are able to obtain sharp and intense emission from the type II heterostructure. The nanocavity was fabricated in a suspended thin film photonic crystal. The defect cavity was specially designed to have the desired cavity mode with a high Q value. E-beam lithography, dry etching and selective wet chemical etching were used to fabricate the nanocavity. The emission spectrum was measured by a micro-photoluminescence system using optical pumping. At 77K, an emission peak at 1004nm with a very high Q factor of 15170 was obtained. To our knowledge, this is the first time that a type-II heterostructure emission was coupled to a photonic nanocavity with a very sharp emission and a high Q value.