Efficient optical limitation is demonstrated in the toluene solution of C60based on the reverse saturable absorption. The highly nonlinear absorption can be used to smooth a spike‐like pulse in the nanosecond region. Optical bistability is obtained in a nonlinear Fabry–Perot cavity filled with a thin layer of polystyrene doped with C60/C70. A smooth pulse with 25 ns width (full width at half‐maximum) is compressed to 15 ns and a spike‐like pulse is subjected a wave form distortion by this device. The light limitation effect in this polystyrene layer 0.3 mm thick was demonstrated at the wavelength of 532 nm and the threshold about 20 mJ/cm2.