In this work, Ni thin films with different thickness from $1,523{AA};to;9,827{AA}$ were deposited for the application of micro thermal flow sensors by a magnetron sputtering and oxidized through annealing at $450^{circ}C$ with increasing annealing time. The initial variation of resistivity decreased radically with increasing films thickness, then gradually stabilizes as the thickness increases. The resistivity of Ni thin films with $3,075{AA}$ increased suddenly with increasing annealing time at $450{circ}C$, then gradually stabilizes as the thickness increases after the annealing time 9 h. In case of $3,075{AA};and;9,827{AA}$ films, the average of TCR values, measured for the operating temperature range of $0^{circ}C;to;180^{circ}C$, were $2,413.1ppm/^{circ}C;and;4,438.5ppm/^{circ}C$, respectively. Because of their high resistivity and very linear TCR, Ni oxide thin films are superior to pure Ni and Pt thin films for flow and temperature sensor applications.