Abstract: The object is to analyze theoretically and test experimentally the pro pagation characteristic of u ltraviolet laser pulse in stepindex multimode fiber.　Experimental results sho w that with the picosecondlevel output laser pulse from fiber,　the power supp ortability of that fiber is confined. on the other hand,　when nanosecondlevel output laser pulse passes tens of meters through fiber,　It is a useable propag ation medium.