Ultrashort-pulses with a duration of several optical cycles are very important in intense field physics research. 0.1 TW/5 fs laser pulses have been generated successfully. However, the high intensity ionization of medium limits the pulse energy of the self-phase modulation in single-mode fiber and hollow fiber filled with noble gases. G. Tempea and T. Brebec suggested that plasma nonlinearity can be used to compress the pulse. The possibility of compressing a 50 fs pulse of about 10 mJ is investigated and the pulse compression involved in the ionization on the inner face of a hollow fiber is discussed in this paper. Based on numerical simulation, it is found that the pulse can be compressed to 5 fs in a lower density gas. So it is possible by decreasing the gas density to reduce the electron density because too much electrons will destroy pulse shape.