$RuO_2$ thin films were prepared with various deposition conditions by rf magnetron sputtering. The films were annealed in vacuum, air, and air-vacuum, after that, the structural and electrical properties of the films were investigated. As the substrate temperature increases, the preferred orientation of the films changes from (101) to (200), and the grain size increases; especially, at $500^{circ}C$, the size considerably increases. The preferred orientation of the films changes from (200) to (101) and the roughness of surface increase with the increase in oxygen partial pressure. The lowest value of resistivity of $RuO_2$ we prepared is $1.5 imes 10^{-5}Omegacodt extrm{cm}$ at the conditions of $400^{circ}C$ and 10% of oxygen partial pressure. After the processes of annealing, the films deposited at $400^{circ}C$ and a oxygen partial pressure of 10% were relatively stable. The films deposited at $500^{circ}C$ have denser structure and smoother surface when the films are annealed in vacuum after annealing in air.