Abstract: To improve the sensitivity of the secondary ion mass spectrometer (SIMS), the secondary neutral particles was introduced, which was generated by the femtosecond laser ionizing the primary ion bombardment with the instantaneous power of 7×10¹⁸ W/cm². In this experiment, the primary ion of oxygen shotted the surface of the sample with 15 keV energy and 45° angle, which was made of pure silver and pure copper. About 1.2 mm above the sample surface, the femtosecond laser was introduced and the secondary neutral particles were ionized by the former. With the impact of the extraction electrode electric field, the ion was bombarded by the primary ion and the laser post-ionization ion were simultaneously introduced perpendicular to the sample surface for the independent research and development time-of-flight mass spectrometry (TOF-SIMS), and then was caught and analyzed by the ion detector. It showed that the counting intensity of the ¹⁰⁷Ag⁺ and ¹⁰⁹Ag⁺ ionized by the femtosecond laser ionizing was about 2 600 cps, and that of the ¹⁰⁷Ag²⁺ and ¹⁰⁹Ag²⁺ was about 200 cps. At the same time, the counting intensity of the ¹⁰⁷Ag⁺ and ¹⁰⁹Ag⁺ ionized by the primary ion bombardment was about 40 cps. The Ag intensity of the neutral particles generated by the femtosecond laser ionizing was seventy fold as much as that generated by the primary ion. And the result demonstrated that the sensitivity of the SIMS could be remarkably improved by the femtosecond laser post-ionization counting. The error of the isotope ratio of the ¹⁰⁷Ag⁺ and ¹⁰⁹Ag⁺ ionized by the femtosecond laser was 0.8%, while that of the ¹⁰⁷Ag²⁺ and ¹⁰⁹Ag²⁺ was 5.8%, and that of ¹⁰⁷Ag⁺ and ¹⁰⁹Ag⁺ ionized by the primary ion bombardment was 5.7%. It was because the femtosecond laser ionized the Ag particles mainly to the monovalent ¹⁰⁷Ag⁺ and ¹⁰⁹Ag⁺ and the quantity of the bivalent ¹⁰⁷Ag²⁺ and ¹⁰⁹Ag²⁺ were fewer compared to the monovalent ones. The productive rate was in the same order of magnitudes compared to that generated by the primary ion bombardment, and the fewer productive rate directly impacted the measurement accuracy of the instrument. Because the productive rate of ¹⁰⁷Ag⁺ and ¹⁰⁹Ag⁺ ionized by the femtosecond laser was much greater than those two formers, the isotope ratio was more approximate to the theoretic result. Therefore it demonstrated that the adhibition of the femtosecond laser greatly improved the productive rate of the secondary ion and the instrument measurement accuracy, which helped the quantitative analysis becoming easier. When the energy of primary ion was 15 keV, to delay the time between the primary ion and the post-ionization laser, the spatial and velocity distribution of the neutral particles generated in the bombardment could be gained, which was according with the Maxwell-Boltzmann distribution. The most probable speed of the Ag neutral particles was about 660 m/s, and that of Cu neutral particles was about 730 m/s. It proved that the most probable speed of the neutral particles was decreasing with the increasing of the sample relative quality. The successful application of femtosecond laser post-ionization could improve the sensitivity of the SIMS, and avoid the impact of matrix effect, which could improve the SIMS accuracy of the quantitative analysis of the trace even the ultratrace element in the geologic sample. Therefore it could promote the wider use of SIMS in geologic fields such as geological dating, vertical distribution of film material, strain silicon material analysis, distribution of isotope abundance of Cr in meteorites, and so on.