Laser trigger weakly coupled plasma in the ultrafast time (10 ~100 fs), modalities and mechanisms to generate ions has been a very difficult problem to ascertain and calculate.Using laser Ionization atoms basic characteristics, find out all the ionization path producing ions which produce ionizing X-ray at the same time, mark and study them. Combined with the nature of the level shift of atoms or ions in the weakly coupling plasma environment. Compare and calculate the method of different ionization which in the same results under the same path. We can distinguish the different ionization order with the same product. A list is given by the calculation and the corresponding characteristic X-ray spectra generated to determine the production process within 10 ~ 100 fs ions as well as mechanisms, ionization path and method of producing ionizing order. Laser-matter interaction physics study provides a detectable technology in short time (10 ~100 fs).