Some resent works in Japan on the standardization of the measurement of total carbonate (TCO2) arereviewed. Themeasurement method and thestandard areneeded to setconsistent and traceable among each labs to keep uncertainties of the data within few μmol/kg in worldwide scale. A experimental work to make a standard of total carbonate based on natural sea water is introduced. The results of the time series measurement improves that the sea water standard keeps its concentration ofTCO2 over 80 days with the variability of ± 1.4 μ mol/kg. Some ex amples of the intercalibration works in Japanese labs show that there are complex and unique systematic offsets between each lab’s data. Thus it is recommended that a consistent program of the intercalibaration study for total carbonate is needed to put forward.