We investigated the growth process and dislocation generation of GaAs1-xNx alloys grown on GaAs by solid-source molecular beam epitaxy (MBE). It was found that the GaAs1-xNx alloys with a mirror-like surface can be grown by lowering the arsenic-to-gallium flux ratio compared to that in the growth of GaAs. The nitrogen composition in the GaAs1-xNx alloys increased with decreasing substrate temperature and with increasing RF-power. As the nitrogen composition increased, the misfit dislocations were observed at the GaAs1-xNx-GaAs heterointerface. It was clarified that the propagation of dislocations was suppressed in GaAs1-xNx alloys by adding nitrogen.