Femtosecond pump-probe technique assisted by surface plasmon resonance （SPR） is investigated numerically in this paper. Our calculations show that the signal ratio ΔR/R is increased by 2—3 orders of magnitude higher than the standard pump-probe technique， where ΔR　and　R are the intensity change and total intensity of the probe beam， respectively. It should also be pointed out that ΔR/R is sensitive to the incident angle of the pump beam and the thickness of the metal film. In particular for the metal-absorbing material system， ΔR induced by the hot electrons in the metal is only 2 percent of that induced by excited absorbing material， so ΔR/R is mainly related to the dynamics of the absorbing material. This technique will be interesting in investigating the ultrafast surface dynamics of thin films.