The invention relates to the field of oil gas, especially to a determination method and a determination apparatus for noble gas isotope in crude oil. According to the invention, a crude oil sample is pre-purified, and the pre-purified sample mainly comprises a noble gas component and does not pollute an instrument, thereby avoiding baking and vacuum-pumping of a system after sample determination each time and substantially increasing the utilization rate of the instrument. The pre-purified sample almost does not contain any organic component, so a background is reduced, influence of organic fragment ions on measurement results is eliminated, and accuracy of test data is improved; organic ingredients in released gas of crude oil are effectively prevented from polluting a high vacuum noble gas isotope mass spectrometer, the superposition effect of organic fragment ion peaks on a target ion peak is reduced, so isotope detection precision is effectively improved. The technological difficulty that noble gas isotope in a crude oil sample is difficult to detect is overcome. Gas-oil-source ternary noble gas isotope data comparison is realized. Accurate and reliable noble gas isotope data are provided for oil gas tracing, oil source comparison and gas source comparison.