  We carry out a systematic study of the response of companion stars in massive
binaries after being impacted by supernova ejecta. A total of 720 1D stellar
evolution calculations are performed to follow the inflation and contraction of
the star in response to the energy injection and how it depends on various
parameters. We find that the maximum luminosity achieved during the inflated
phase is only dependent on the stellar mass and we derive an analytic formula
to describe the relation. There is also a tight correlation between the
duration of expansion and the intersected energy. These correlations will be
useful to constrain pre-supernova binary parameters from future detections of
inflated companions. We also discuss the possible outcomes of the binary system
when the companion inflation is taken into account. Based on simple binary
population synthesis, we estimate that $\sim$1-3% of stripped-envelope
supernovae may have observable inflated companions. Finally, we apply our
models to the observed companion of SN2006jc and place strong constraints on
the possible pre-supernova binary parameters.
