Recently optical-microwave interactions in the yttrium iron garnet (YIG) film have been extensively studied due to its importance in the new, high speed optical signal processing devices. In this work, we present the experimental results on the simultaneous operation of optical isolator and optical modulator in a microstrip line on YIG single crystal. Optical isolation of more than 20 dB has been observed experimentally together with optical modulation by magnetostatic backward volume wave (MSBVW) in the frequency range from 1.5 GHz to 4.5 GHz. Theoretical results on the combined isolator-modulator in magneto-optic media based on the tensor form of dielectric constant are also discussed.