In this study, the effect of $Nb_2O_5$ and sintering time on the positive temperature of coefficient of resistivity (PTCR) behavior of lead free $Ba_{0.99}(Bi_{0.5}Na_{0.5})_{0.01}TiO_3$ (BBNT) ceramics were investigated in order to fabricate a PTC thermistor with high $T_c$ temperature more than $140^{circ}C$. In particular, BBNT ceramic doped with 0.1mol% $Nb_2O_5$ and sintered at $1350^{circ}C$ for 4 h has significantly increased Curie temperature ($T_c$) of about $200^{circ}C$, showed good PTCR behavior of room-temperature resistivity ($ ho_{rt}$) of $40{Omega}{cdot}cm$, a high $ ho_{max}/ ho_{min}$ ratio of $43.78{ imes}10^3$ and a large resistivity temperature factor (${alpha}$) of 16.1%/$^{circ}C$. With increasing addition of $Nb_2O_5$ content, the $ ho_{rt}$ decreased to a minimum value of $40;{Omega}cm$ at 0.1mol% $Nb_2O_5$ and the $ ho_{rt}$ increased for x value over 0.1 mol%.