Based upon a new charge moment tensor and the calculation rule of magnetic moment for a rotational charged body

and by means of Euler’s angular coordinates and Euler’s kinetic equation about a rotational rigid body in classical mechanics

the general Lagrangian and Euler’s dynamic equation of a charged dielectric rigid body under a uniform magnetic field have been derived.According to the test rule for a vector to make regular precession

one simple case of regular precession involved in a rotational charged rigid body in a uniform magnetic field is verified and the precession angular velocity is calculated.The concrete Lagrangian and Lagrange equations are also derived and discussed in detail for another symmetric case

whose corresponding invariants have also been found.