  We investigate the second order energy density perturbation $\delta^{(2)}$
induced by small-scale Gaussian and local-type non-Gaussian primordial
curvature perturbations. The relative abundance of primordial black hole is
calculated in terms of the probability density function of total energy density
perturbation $\delta_r=\delta^{(1)}+\frac{1}{2}\delta^{(2)}$. The effects of
second order density perturbation greatly reduce the upper bounds of
small-scale power spectra of primordial curvature perturbations by one to two
orders of magnitude. For log-normal primordial power spectrum, its amplitude
$A_{\zeta}$ is constrained to be about $A_{\zeta}\sim 3\times10^{-3}$. And for
local-type non-Gaussianity with $f_{\mathrm{NL}}=10$, the upper bound of
$A_{\zeta}$ is about $2.5\times10^{-4}$.
