  In this paper, the behaviour of a charged massive scalar test field in the
background of a Kerr-Sen black hole is investigated. A kind of stationary
solutions, dubbed scalar clouds, are obtained numerically and expressed by the
existence lines in the parameter space. We show that for fixed background and a
given set of harmonic indices, the mass and charge of the scalar clouds are
limited in a finite region in the parameter space of the scalar field.
Particularly, the maximum values of the mass and charge of the clouds around
extremal Kerr-Sen black holes are independent of the angular velocity of the
black hole, whereas those in the extremal Kerr-Newman background depend on the
angular velocity. In addition, it is demonstrated that, as the static limit of
Kerr-Sen black hole, Gibbons-Maeda-Garfinkle-Horowitz-Strominger black hole can
not support scalar cloud.
