  Stellar population synthesis is an important method in the galaxy and
star-cluster studies. In the stellar population synthesis models, stellar
spectral library is necessary for the integrated spectra of the stellar
population. Usually, the stellar spectral library is used to the transformation
between the stellar atmospheric parameters and the stellar spectrum. The
empirical stellar spectral library has irreplaceable advantages than the
theoretical library. However, for the empirical spectral library, the
distribution of stars is irregularly in the stellar atmospheric parameter
space, this makes the traditional interpolator difficult to get the accurate
results. In this work, we will provide an improved radial basis function
interpolator which is used to obtain the interpolated stellar spectra based on
the empirical stellar spectral library. For this interpolator, we use the
relation between the standard variance {\sigma} in the Gaussian radial basis
function and the density distribution of stars in the stellar atmospheric
parameter space to give the prior constraint on this {\sigma}. Moreover, we
also consider the anisotropic radius basis function by the advantage of the
local dispersion of stars in the stellar atmospheric parameter space.
Furthermore, we use the empirical stellar spectral library MILES to test this
interpolator. On the whole, the interpolator has a good performance except for
the edge of the low-temperature region. At last, we compare this interpolator
with the work in Cheng et al. (2018), the interpolation result shows an obvious
improvement. Users can use this interpolator to get the interpolated spectra
based on the stellar spectral library quickly and easily.
