Theoretical MHD analyses of the Large Helical Device (LHD) plasmas have progressed extensively. Recent results with respect to three-dimensional equilibrium, linear stability, and nonlinear dynamics are presented. Magnetic island variation due to finite-beta effect, the second stability of ballooning modes and related features, self-organization in nonlinear evolution of interchange modes, high-accuracy nonlinear calculation for ballooning modes up to high toroidal wave number, and plasma collapse in the ballooning mode dynamics are discussed.