Abstract
There are several salient features of the charmless three-body baryonic B decays. The so-called threshold effect indicates that the B meson is preferred to decay into a baryon-antibaryon pair with low invariant mass accompanied by a fast recoil meson.This effect can be understood in terms of a simple short-distance picture. One energetic q\bar q pair must be emitted back to back by a hard gluon in order to produce a baryon and an antibaryon in the two-body decay. The study of the charmful baryonic B decays may help improve our understanding of underlying mechanism for threshold enhancement and the angular distribution in the three-body decays. Theoretically, the relevant topologic quark diagrams for charmful decays are simpler than the charmless ones as the latter receive not only tree bot also penguin contributions. In this thesis,we shall therefore focus on B \to \mathbf{B \bar B'}M_c with M_c = D^(*) or J/\psi, and our first task is to see if we can explain the branching fractions.