The action of a normal pulsed ruby laser beam on a mercury plate has been investigated. It was predicted from qualitative consideration that its oharaot eristics of light transmission and reflection depend not only on the light energy density butalso on the internal pressure of the mercury plate. The front part of the acting laser pulse was absorbed and the transmission light corresponded to the pulse-tail. The phenomenon observed in our experiments is helpfu] to intarpret the mechanism of light transmission through a meroury plate. This paper reports experimental phenomenon observed in our work and makes an analysis to them.