Taurine in food was separated by HPLC as its phthalaldehyde-ethanethiol derivative on mu-Bondapak C18 reverse column and measured at 330 nm. The determination was not interfered by sulphosalicylic acid, excess dervatizing reagents and 20 kinds of amino acids. The stability of the taurine dervatives was discussed in this paper. The result showed that the higher concentration of borate buffer, the more stable of taurine derivatives and the lower concentration of taurine, the faster decomposition of taurine dervitives. Using more concentrated borate buffer (0.4 mol/L) and controlling the time between injection and reaction and keeping the operation identically could avoid the effect of nonstable taurine derivatives in the determination. The minimum detectable quantlity was 8 ng. The coefficient of variation was less than 8%. The recoveries were 90.7%-105.1%.