A theoretical Treatment is presented on the propagation characteristics of magnetostatic forward volume waves and related guided-wave magnetooptic (MO) Bragg diffraction in an YIG-GGG waveguide under an inclined bias magnetic field.It is found that,in contrast to the usual situation of a perpendicular bias magnetic field,an inclined bias magnetic field leads to the modification to the phase matching condition and,as a result of increased Faraday effect etc.,facilitates enhancement of MO Bragg diffraction efficiency.Such an efficiency enhancement enables utilization of low-propagation loss materials such as the pure YIG for construction of viable guided-wave MO Bragg devices.The theoretical predictions are in good agreement with the experimental results.