The effect of temporally-splitting high pressure injection on Diesel spray combustion and soot formation processes was studied by using the high-speed video camera. The spray was injected by the single-hole nozzle with a hole diameter of 0.11mm into the high-pressure and high-temperature constant volume vessel. The free spray and the spray impingement on the two dimensional (2D) piston cavity wall were examined. Injection pressures of 100 and 160 MPa for the single injection and 160 MPa for the split injection were selected. The flame structure and soot formation process were examined by using the two-color pyrometry. The soot generated in the flame under the split injection under 160 MPa becomes higher than that of the single injection under 160 MPa. However when comparing between the split injection of 160 MPa and the single injection of 100 MPa, the split injection reduces the soot in the free spray, whereas the split injection increases the soot in the two dimensional (2D) piston cavity impinging spray flame. The high pressure split injection shows an ability to reduce soot faster than that of the single injection under the same injection pressure.