Chloride in human body fluids is physiologically important. In this paper, chloride in human body fluids, including blood serum, urine, and cerebrospinal fluid (CSF), was determined by ion chromatography with a serial piezoelectric quartz crystal (SPQC) as detector, and 2.0 mmol/L potassium hydrogen phthalate (KHP) as mobile phase. Also discussed was sample pretreatment for the determination. The method is rather simple, rapid, accurate, and reproducible. Body fluids of patients were analyzed using both the presented method and classical method, and the obtained results well agreed with each other.