We report a Brillouin optical time domain analyzer (BOTDA) based on bi-directional Raman amplification in this paper. With the bi-directional Raman amplification, the loss of the optical fiber and the depletion of Brillouin pump light can be compensated for efficiently, hence the measurement resolution is improved at the end of the optical fiber significantly. The detected signal is stable along the whole length of the sensing fiber, free from the spectral broadening caused by the modulation instability and the problem of uneven ness of detected signals of the conventional BOTDA. The Raman amplification is very useful for enhancing the measurement accuracy. With the bi-directional Raman pump, a temperature resolution of 0.6 ℃ was achieved over a sensing distance of 50 km with a 50 m spatial resolution. The signal-to-noise ratio and the optical signal power distribution characteristics of the system have been studied by experiment.