Platinum-Cobalt alloy thin films were deposited on $Al_{2}O_{3}$ substrate by magnetron cosputtering for RTD temperature sensors. We made Pt-Co alloy resistance patterns on the $Al_{2}O_{3}$ substrate by lift-off method and investigated the physical and electrical characteristics of these films under various conditions, the input power, working vacuum, annealing temperature and time, and also after annealing these films. The resistivity and sheet resistivity of these films were decreased with increasing the annealing temperature. At input power of Pt : $4.4;W/cm^{2}$, Co : $6.91;W/cm^{2}$, working vacuum of 10 mTorr and annealing conditions of $800^{circ}C$ and 60 min, the resistivity and sheet resistivity of Pt-Co thin films was $15{mu}{Omega}{cdot}cm$ and $0.5{Omega}/{square}$, respectively and the TCR value of Pt-Co alloy thin films with thickness of $3000{AA}$ were $3740ppm/^{circ}C$ in the temperature range of $25{sim}600^{circ}C$. These results indicate that Pt-Co alloy thin films have potentiality for the RTD temperature sensors.