The invention discloses a novel uranium isotope ratio measuring device which mainly comprises a first detection laser, a second detection laser, a beam combiner, an ablation laser, a beam splitter, a first photoelectric detector, a second photoelectric detector, a data acquisition card and an industrial personal computer. Ablating laser emitted by the ablating laser irradiates a sample in the ablating chamber through the second reflecting mirror to excite plasma, laser emitted by the first detecting laser passes through the first polarizing film, laser emitted by the second detecting laser passes through the first reflecting mirror and the polarizing film in sequence, the two beams of laser are combined by the beam combiner and then pass through the plasma, the beam splitter re-splits to the first photoelectric detector and the second photoelectric detector, and the data acquisition card acquires signals of the first photoelectric detector and the second photoelectric detector and transmits the signals to the industrial personal computer. The invention further discloses a novel uranium isotope ratio measuring method. The invention provides a technology which is portable, rapid, high in sensitivity and capable of measuring the uranium isotope ratio in a non-contact mode.