  HLX-1, currently the best intermediate-mass black hole candidate, has
undergone seven violent outbursts, each with a peak X-ray luminosity of
$L_{\mathrm{peak},\mathrm{X}}\sim 10^{42}\ \rm{erg\ s^{-1}}$. Interestingly,
the properties of the HLX-1 outbursts evolve with time. In this work, we aim to
constrain the physical parameters of the central engine of the HLX-1 outbursts
in the framework of the black hole accretion. We find that the physical
properties of the HLX-1 outbursts are consistent with being driven by the
radiation pressure instability. This scenario can explain the evolution of the
recurrent timescales of the HLX-1 outbursts as a function of the durations.
