  Galactic microlensing has been widely used to study the star and planet. The
stellar wind plays an important role in the formation, environment and
habitability of the planet. In this work we study a binary microlensing system
including the stellar wind, i.e. a star with plasma environment plus a planet.
Plasma surrounding the main lens causes chromatic deflection of the light rays,
in addition to the gravitational one. As a result, such a lensing system can
generate complicated caustics which depends on the different lensing
parameters. In this work we study the magnification curves for different traces
of the background source and compare the transitions of the formation of ``hill
and hole'' in the magnification curves. We find that the plasma will cause
extra caustic, shrink the central caustics generated by the star and push the
caustic by the planet outwards. Observations and modelling of binary
microlensing curves with taking plasma effect into account can provide a
potential method to study plasma environment of the stars. In case of a high
plasma density of the stellar wind, the plasma lensing effects will be
observable in the sub-mm band.
