Kane's method and algebraic vector representation are utilized to construct a new equation of motion for constrained multirigid-body systems. This new equation is called "matrix equation of motion for constrained multirigid-body systems" and can be used conveniently to derive the equations of motion for each application model. It can also be used as a basic equation for creating new methods of simulation, as well as design or control problems. A simple example is given to illustrate how this equation is used.