The invention discloses an evaluation method for judging water-oil-gas distribution in a petroleum and natural gas reservoir stratum. A novel gas logging and gas interpretation and evaluation method which has certain application range and is prior to a Pixler method in the judgment of a gas reservoir, an oil reservoir, a water-oil reservoir and a water reservoir of the reservoir stratum is summarized according to three gas ratios, namely C2/C1 (the ratio of ethane to methane), C3/C1 (the ratio of propane to methane) and C4/C1 (the ratio of butane to methane) by using statistic analysis of field gas logging and well completion oil testing data of a petroleum and natural gas exploration and development well. The evaluation method has the advantages of simpleness, practicality, higher coincidence rate and wide application range. Particularly, the evaluation method has unique technical advantages of quickly and accurately obtaining the characteristics of water, oil and gas contained in an underground reservoir stratum by drilling in the logging while drilling operation process of petroleum and natural gas exploration and development.