The traditional fiber distributed temperature sensor has the shortcoming of low precision and expensive equipments. New distributed temperature sensor based on stimulated Brillouin scattering (SBS) is designed by filling alcohol in photonic crystal fiber (PCF). Since the refractive index of alcohol varies with temperature, which results in the effective mode area of PCF varying with temperature, the output power of pulse in fiber varies with temperature. The coupled amplitude equations of SBS in optical fiber are solved numerically. And the relations between output power and temperature are obtained. The possibility of new sensing mechanism is proved. In order to achieve a precision of 1 ℃ for the new design, the dynamic range of power measurement equipment is only 40 dB, which is far less than that of frequency measurement equipment in traditional measurement system. Some influence factors in the new system are also analyzed.