A visualization experimental apparatus with high speed controlled flash photography techniques was developed to investigate the flow in the hole of diesel injection nozzles and the spray construction near orifice. The experiments were performed with the transparent actual nozzles for diesel,gasoline,ethanol diesel fuel and biodiesel. The results indicate that the cavitation films could be observed in the hole for all fuels. The initial cavitation was appeared earlier and the cavitation intensity was stronger for the fuel which had lower viscosity and higher saturated vapor pressure. There was larger spray cone angle with stronger cavitation intensity. After the jet was finished, the gas backflow phenomenon could be observed in the hole and the initial bubble would be produced. And the initial bubble size could increase with the reduction of fuel surface tension. The flow status in the pressure chamber and hole was greatly affected by the movement of needle.