用平衡相交的Landau平均场理论，分别考察了两个在相干光驱动下的耗散系统(即化学反应系统和Josephson结)中的光学双稳性及其临界现象。揭示了作为类一级相交终止点的双稳性转变点具有二级相交的特征.同时也揭示了这两个物理内容完全不同的系统在该临界点附近的共性.

The critical phenomena of optical bistability in two dissipative systems, i. e. the chemical reaction system and the Josephson junction, both driven externally by coherent light field, are examined by Landau (mean field) theory of phase transition in equilibrium thermodynamics. It is revealed that the critical point of bistability as an end point of firstorder-like transitions possesses the features of phase transition of second order. And the generality in the neibourhood of this critical point of these two systems with very different physical contents is illustrated also.