Abstract: Based on the Dirac-Maxwell＇s equations and generalized Lorentz force formula, the concepts and meaning of magnetic monopole and electromagnetic duality are introduced and discussed. According to the electromagnetic duality,the Maxwell＇s equations and Lorentz force formula can be transformed into a new form with coexistence of electric charges and magnetic charges,but the conjecture of Dirac monopole changes significantly the structure of Maxwell＇s equations, so that no duality transformation can reduce the Dirac-Maxwell＇s equations to the original form of Maxwell＇s equations. By using the generalized Lorentz force formula,it is also proven that both of the Dirac-Maxwell field and Maxwell electromagnetic field share the same formulae of energy density,Poyinting vector, density of kinetic momentum and tensor of kinetic momentum flow. Finally, we state that the fields of Dirac- Maxwell＇s equations can be decomposed into two groups of Maxwell＇s equations, one for electrical charges and the other for magnetic charges,and therefore the problem of monopole can be described and solved by employing the traditional theory of electrodynamics.

Key words: Dirac-Maxwell＇s equations, generalized Lorentz force formula, magnetic monopole, electromagnetic duality