Room-temperature strong exciton-photon coupling phenomena was studied in a low-finesse quantum microcavity entirely filled with 17.5 pairs of GaAs (80 Angstrom )Al0.3Ga0.7As (42 Angstrom) quantum wells. The front and back distributed Bragg reflectors of the microcavity consist of only 6 and 8 pairs of lambda /4 stacks of GaAs (30 Angstrom)/AlAs (5 Angstrom) superlattices and AlAs layers. And the lambda /4 GaAs (30 Angstrom)/AlAs (5 Angstrom) superlattices are equal to the Al0.2Ga0.8As layer in thc distributed Bragg reflector. Large Rabi splitting of 9.4meV was observed at resonance with heavy-hole excitons at room temperature. Photoluminescence spectra show cd a transition from linear regime to high carrier density nonlinear regime due to loss of oscillator strength and collapse of the coupling at high excitation intensity.