In this paper we assume that the signal injected into ring cavity laser have a transverse distribution of the TEM10 mode. Using the method of mean field approximation, we obtained the steady state equation and performed linearized stabililty analysis under the one transverse mode resonant condition. The result showed that for the good cavity case the output of laser with a injected signal having a transverse distribution of the TEM10 mode exhibits a bistability, and this is different from the case discussed by Lugiato at al in which the signal injected into ring oavity laser 15 a plane wave beam and a Gaussian beam (TEMqo mode) respectively.