Based on a light source with adjustable pulsewidth,a dual functional fiber Raman distributed temperature sensor was proposed.Short pulses were used to achieve high spatial resolution for peak temperature detection.Wide pulses were adopted to obtain high temperature resolution for average temperature monitoring.The proposed method can achieve either high spatial resolution or high temperature resolution for various applications.The experimental results indicate that the measurement time can be saved greatly for the same temperature resolution comparing to the conventional method with constant pulsewidth.