Bubble elecrospinning is an excellent and novelty method to fabricate nanofibres with high throughout. This paper investigates experimentally the effects of solution concentration and its viscosity on diameter and morphology of bubble electrospun polyvinyl alcohol (PVA) nanofibres, where pure water is used as a solvent for environmental consideration. The experiment shows that the as spun fibres change their morphology from few beads, smooth surfaces and finally to larger diameter fibres when PVA solution concentration increases gradually. An allometric relation between the fibre diameter and the solution concentration is obtained. The minimal diameter is as small as 38.3 nm.