Simultaneous growth of different kinds of aligned GaN nanostructures (i.e., nanowires, needles, pyramids and micro-rods) on a single substrate was firstly realized at a low temperature of 790 °C by naturally changing the III/V ratio across the substrate via a coaxial pipeline configuration. The effects of substrate distance and growth pressure on nanostructure growth were investigated. The morphology variation from nanowires to micros-rods would be explained in terms of Ga species changing from the Ga element to GaN molecule in a hot-wall reactor. This work is helpful for on chip integration of different kinds of nanodevices on unusual substrates of low melting temperature.