In this work, the corrosion and passive behavior of Ti-3Mo titanium alloy with various annealing temperatures from 750 °C to 1050 °C in 20 wt% hydrochloric acid solution is investigated via electrochemical measurements, static immersion test, X-ray photoelectron spectroscopy and scanning electron microscopy. The results show that the corrosion rate increases with an increase in annealing temperature, which is attributed to the accelerated dissolution of the passive film after the annealed temperature above 850 °C and the formation of microgalvanic cells by α- and β-phase. Moreover, the passive film displays the n-type semiconductor properties independent of annealing temperature.