The fuel spray images were taken with an equipment (camera-flash-injection) which has been synchronized with a purpose made electronic system under the condition of the high pressure common rail in two injection pressure has been expressed in this paper. It is discovered when fitting spray tip penetration that after jet breakup for a period of time, the spray tip begin to slow down rapidly, and the speed of spray tip running becomes smooth. Hiroyasu and other traditional tip penetration fitting formula are fitting larger to this phase. This is because that after jet breakup, the secondary breakup of striker particles will occur under the influence of the aerodynamic, surface tension and viscosity force. Therefore, a spray penetration fitting formula containing secondary breakup time to fit penetration in three sections was proposed in this paper. Results show that when pressure difference increase, both first and second breakup time become earlier. The former is because of gas-liquid relative velocity increasing, while the latter is due to high speed interface movement acceleration increasing.