Abstract: Following the Interlaboratory Comparison (ILC) completed in WMO RA Ⅵ under the MeteoMet project of Europe, a further Interlaboraroty Comparison focusing on atmospheric temperature, humidity and pressure was started in the Regional Instrument Centers (RIC) of WMO RA Ⅱ, Ⅴ and Ⅵ.The ILC was performed in a round-robin scheme, with a single loop.Every pilot laboratory performed two sets of measurements, at the beginning and at the end of the loop.And the participating laboratories performed their measurements in between.According to the ILC, the reference value for calculation was based on the weighted mean from the pilot laboratories.In this paper, it is proposed that the reference value for calculation be based on the weighted mean from all laboratories.Using the comparison results from each laboratory, two reference values were determined by different algorithms.And the measurement results of each laboratory were evaluated with reference to E_n numbers.Furthermore, The effects of two reference values on the evaluation results were compared to verify the data compatibility between the participating laboratory and the pilot laboratory in terms of the unsatisfying results from some measurement points of the former.The analysis shows that, compared to the calculation method that takes the weighted mean from the pilot laboratories as the reference value, it is more reasonable and equitable to take the weighted mean from all the laboratories as the reference value.