Clinical biochemical items such as alanine amino-transferase(ALT), Creatinine(Cr), total protein(TP) in serum were analyzed by using ZS-3 semi-automatic biochemical analyzer. The results show that the machine had a good precision. The mean intra-assay deviation CV was under 5% and mean inter-assay deviation CV was under 9%. The average recovery was 95%～105%. When the drawn liquid volume was over 500 μl, the cross contamination could be controled under 5%～2%.