  We investigate the production of CP-odd Higgs boson $A^0$ associated with a
real $\gamma$ in $e^+e^-$ collisions. Because of the properties of $A^0$
coupling to the other fields, the main contribution comes from the top-quark
triangle loop diagrams. We obtain the timelike transition form factor which
describes the production amplitude of $A^0$ in the $e^+e^-$ collisions. This
timelike transition form factor is related to the spacelike transition form
factor relevant for the $A^0$ production in $e^-\gamma$ collisions. It turns
out that the possible extra contributions from chargino-sneutrino and
neutralino-selectron box diagrams do not give sizable effects.
