The present invention discloses a speed measuring device used for RM instability test gas-liquid interface with improved measurement precision, which comprises an oscilloscope, more than two gas-liquid interface monitors and more than two signal amplifiers, wherein each gas-liquid interface monitor comprises a laser emitter and an electro-optical signal converter arranged on a light path of the laser emitter; the light paths of all the laser emitters are parallel; the electro-optical signal converters are electrically connected with the input ends of the corresponding signal amplifiers respectively; and the output ends of the signal amplifiers are electrically connected with the oscilloscope. The speed measuring device used for RM instability test gas-liquid interface with improved measurement precision provided by the present invention has reasonable structure, convenient and rapid measurement and high measurement precision and can eliminate the shooting error of a high-speed shooting method in the prior art.