  In this paper we collect 19 hydrogen-deficient superluminous supernovae
(SLSNe) and fit their light curves, temperature evolution, and velocity
evolution based on the magnetar-powered model. To obtain the best-fitting
parameters, we incorporate the Markov Chain Monte Carlo approach. We get rather
good fits for 7 events ($\chi^2$/d.o.f = $0.24-0.96$) and good fits for other 7
events ($\chi^2$/d.o.f = $1.37-3.13$). We find that the initial periods
($P_{0}$) and magnetic strength ($B_{p}$) of the magnetars supposed to power
these SLSNe are in the range of $\sim 1.2-8.3$ ms and $\sim (0.2-8.8)\times
10^{14}\,$G, respectively; the inferred masses of the ejecta of these SLSNe are
between 1 and 27.6 $M_{\odot }$, and the values of the gamma-ray opacity
$\kappa_{\gamma }$ are between 0.01 and 0.82 cm$^2$ ~g$^{-1}$. We also
calculate the fraction of the initial rotational energy of the magnetars
harbored in the centers of the remnants of these SLSNe that is converted to the
kinetic energy of the ejecta and find that the fraction is $\sim 19-97$ for
different values of $P_{0}$ and $B_{p}$, indicating that the acceleration
effect cannot be neglected. Moreover, we find that the initial kinetic energies
of most of these SLSNe are so small ($\lesssim 2\times 10^{51}$ erg) that they
can be easily explained by the neutrino-driven mechanism. These results can
help clarify some important issues related to the energy-source mechanisms and
explosion mechanisms and reveal the nature of SLSNe.
