The energy spectra and oscillator strength of atom Rb in strong magnet
ic fields are calculated. The wavefunctions obtained by an improved po
tential model proposed by some of us are chosen as the zero-order ones
. The results show that the diamagnetic term seems to affect substanti
ally only high Rydberg states. And there is a maximum of oscillator st
rength in each n-manifold, which varies with n increased.