  In this article, the superradiation stability of Kerr-Newman black holes is
discussed by introducing the condition used in Kerr black holes y into them.
Moreover, the motion equation of the minimal coupled scalar perturbation in a
Kerr-Newman black hole is divided into angular and radial parts. Hod
proved\cite{12} that the Kerr black hole should be superradiantly stable under
massive scalar perturbation when $\mu \ge \sqrt{2}m\Omega_H$, where $\mu$ is
the mass. In this article, a new variable y is added here to expand the results
of the above article. When $\sqrt{2(a^2+Q^2)}/{r^2_+}< \omega<
m\varOmega_H+q\varPhi_H$,particularly $\mu \ge
\sqrt{2}(m\varOmega_H+q\varPhi_H)$,so the Kerr-Newman black hole is
superradiantly stable at that time.
