We have further studied experimentally and theoretically the process of conversion from self-defocusing to self-focusing in LiNbO—3:Fe crystals, which was reported in Acta Phys.Sin.[STHZ]50[STBZ] 483. Based on our experimental result, we have proposed a new type of theoretical model of phase conjugate resonant cavity, analyzed the role of the cavity in the process of conversion from self-defocusing to selffocusing. We have also proposed a new type of bright spatial soliton, i.e.,the phase conjugate bright spatial soliton, and indicated that the bright spatial soliton is a mode in the phase conjugate resonate cavity.