The invention provides a method for evaluating and judging the selectivity trend of a catalyst in a synthetic-gas-containing atmosphere. The analytical test by in-situ continuous temperature programmed reduction-temperature programmed oxidation (TPR-TPO) indicates that after acquiring the TPR performance curve and TPO performance curve capable of combined comparison, the selectivity trend of the unknown catalyst sample can be accurately and quickly judged according to the judgment rules in combination with the properties of the known catalyst sample.