  Based on a combination of X-ray diffraction, electrical transports, magnetic
susceptibility, specific heat and pressure effect measurements, we report a
series of BiS$_{2}$-based Sr$_{1-x}$Pr$_{x}$FBiS$_{2}$ superconductors with the
maximum $T_c$ of 2.7 K for $x =$ 0.5 at ambient pressure. Superconductivity can
be only observed at 0.4 $\leq$ x $\leq$ 0.7 while the normal state resistivity
shows the semiconducting-like behaviors. $\chi(T)$ displays the low
superconducting shielding volume fractions and $C(T)$ does not exhibit
distinguishable anomaly around $T_c$, suggesting a filamentary
superconductivity in the Pr-doped polycrystalline samples. By varying doping
concentrations, an electrnoic phase diagram can thus be established. Upon
applying pressure on the optimal doping Sr$_{0.5}$Pr$_{0.5}$FBiS$_{2}$ system,
$T_c$ is abruptly enhanced, reaches 8.5 K at a critical pressure of $P_c =$ 1.5
GPa and remains a slight increase up to 9.7 K up to 2.5 GPa. Accompanied with
the enhancement of superconductivity from the low-$T_c$ phase to the high-$T_c$
phase, the normal state undergoes a semiconductor-to-metal transition under
pressure. The scenario can be linked to the enhancement of orbital overlap of
Bi-6p and S-p, contributing to the bulk superconductivity above $P_c$. Phase
diagram for Sr$_{0.5}$Pr$_{0.5}$FBiS$_{2}$ is also obtained.
