The characteristics of diesel combustion with high pressure fuel injection were investigated, using a naturally aspirated single cylinder engine and a high pressure injection equipment which can produce over 250 MPa injection pressure. Observation and analysis of combustion were performed using a high speed shadowgraph technique, with different injection pressures. In the case of high injection pressure in combination with smaller nozzle hole diameter, generation of soot in the combustion field is hardly recognized. Also by increasing injection pressure, ignition points tend to shift to the downstream of spray. Analysis of flame motion and turbulence intensity in the combustion field was performed using high speed direct photographs and image analysis technique by tracing flame luminosity distribution time history. By increasing injection pressure, an increase of turbulence intensity at the early stage of diffusion burning was observed.