An experimental study has been made of the instantaneous two dimensional visualization of soot distribution profile in a diesel spray flame. The spray flame was formed by a single shot of fuel injection in high pressure and high temperature gaseous environments inside a constant volume combustion chamber. A cross section fo the spray flame was illuminated by a sheet of incident laser light. The images of visible flame and scattered light were recorded simultaneously by using a CCD camera with a gated image intensifier at an arbitrary instant of time after the start of fuel injection. The results showed that the high concentration region of soot existed along the central axis of the spray flame, and that the soot distribution profile was highly heterogeneous. The soot in the spray flame would increase with the lapse of time and would reach a maximum after which it would decrease to a very low value approaching zero. The effects of ambient oxygen concentration, injection pressure and fuel properties on the soot formation were revealed.