This paper reported the method development and validation of a gas chromatography with thermal conductivity detector (GC-TCD) method for the measurement of the gaseous products of hydrodeoxygenation (HDO). The method validation parameters include selectivity, precision (repeatability and reproducibility), accuracy, linearity, limit of detection (LoD), limit of quantitation (LoQ), and robustness. The results showed that the developed method was able to separate the target components (H₂, CO₂, CH₄ and CO) from their mixtures without any special sample treatment. The validated method was selective, precise, accurate, and robust. Application of the developed and validated GC-TCD method to the measurement of by-product components of HDO of bio-oil revealed a good performance with relative standard deviation (RSD) less than 1.0% for all target components, implying that the process of method development and validation provides a trustworthy way of obtaining reliable analytical data.