This paper describes the characteristics of six laser dyes of PBD series which are compounds of 2-phenyl- and five of 2-(p- or m- substitued phenyl)-5-(4 -biphenyl-yl oxadiazoles. Two of them are new compounds that were synthesized by Nankai University. The ultraviolet absorption spectra, fluorescence spectra and fluorescence quantum yields of such dyes are given. Tuning curves of PBD dye lasers pumped by a nitrogen laser are measured, and the tunable spectral regions are found to be of 356 to 393 nm. The laser conversion efficiencies of all the six PBD dyes reported here are higher than those of existing laser dyes of PPO and BPBD. The PBD series dyes are suitable to be pumped by either N2 laser (377nm) or XeGl excimer laser (308nm).