Polysilicon resistors with high thermal stability have been fabricated by a new mixed process using POCl$_{3}$ doping and arsenic implantation. Varous temeprature coefficients, which range form 510 ppm/.deg. C to -302 ppm/.deg. C, were shown from the fabricated polysilicon resistors with sheet resistance of 58~107 .ohm./sq in the operating temeprature of 27~150.deg. C. The temperature coefficient of the polysilicon resistor by the mixed technology was about 4.3 times as low compared to the conventional polysilicon resistor using POCl$_{3}$ doped single process with the same sheet resistance of 75.ohm./sq. In addition, the mixed technology can be applied to obtain nearly zero temperature coefficient for polysilicon resistors which are reliable and insensitive to temperature.