Flexural-torsional buckling or lateral torsional buckling is an important limit state for wood composite I-joist because the in-plane bending stiffness is typically greater than torsional lateral bending stiffness. Web local buckling is another important limit state because of the thin-walled web configuration. To increase the buckling capacities of wood composite I-joist, a new structural wood composite I-joist with sinusoidal web has been developed at West Virginia University. Extensive experimental investigations have been conducted in a companion study (McGraw, 2012). This study presents analytical evaluations of buckling behavior, including flexural-torsional buckling of simply-supported beam and cantilever beam, and local buckling of web panel under compression. Critical buckling loads are predicted using energy method. The analytical results are verified against the experimental results from McGraw (2012) and Finite Element analysis, where good agreement can be observed. The analytical models are further employed to conduct a parametric study to evaluate the effects of the length and height of the I-joist on global flexural-torsional buckling and elastic restraint at the flange-web joint on local compressive buckling of the web panel. The analytical solutions developed in this study can be extended to determine the buckling capacities of I-joist with different web geometries.