We implement an algorithm, termed parallel-processing physical optics, providing an efficient high-frequency approximation method to characterize the scattering of Laguerre-Gaussian (LG) vortex electromagnetic (EM) beams by electrically large-scaled complex targets. The incident beam is described by vector expressions in terms of electric and magnetic fields, and it is combined with rotation Euler angles to achieve an arbitrary incidence of the vortex beam. The validity and capability of the proposed method are illustrated numerically, and the effects of various beam parameters as well as target geometric models such as a blunt cone and Tomahawk-A missile on monostatic and bistatic radar cross section distributions are investigated. Results show that the scattering features of the vortex beam vary significantly with the parameters of the vortex beam and the target. These results are helpful to reveal the scattering mechanism of LG vortex EM beams and provide a reference for the application of vortex beams to detect electrically large-scaled targets.