The experimental study of self- induced coherent light oscillations with photorefractive crystal KNbO3:Fe in a linear cavity are reported. For the transmission of the cavity P=0.28, the incident intensity dependence on the oscillating light intensities I'A, the phase conjugating light intensities IPC, the phase conjugation reflectivity Rc, the oscillating light build-up time constant τ0 and the phase conjugate light build-up time constant τc are measured respectively. For Ip=7.8 W/cm2, the maximum reflectivity Rc=1.6% and the maximum oscillating light intensity IA=2I′A=1.0 W/cm2 are obtained.