An analytical method for determination of tetramethylenedisulfotetramine (tetramine) in human urine by gas chromatography-flame thermionic detection (GC-FTD) coupling with a direct immersed solid-phase micro-extraction (DI-SPME) was developed. The enrichment effects of three fiber coatings of SPME for tetramine were compared. Results showed that the enrichment effect of polar 85 microm polyacrylate (PA) coating was better than that of apolar 100 and 7 microm polydimethylsiloxane (PDMS) coatings. Other experimental parameters, such as ionic strength, volume, temperature of sample solution and time for extraction, time and temperature for desorption, were also optimized. The correlation coefficient of the calibration curve was 0.9998 in the range of 0.082-41.0 ng/mL for tetramine. The limit of quantitation of tetramine in urine was 0.082 ng/mL. In this method, the sample pretreatment is simple and convenient. As a monitoring means, it has been successfully applied to detection of tetramine toxicosis in criminal cases, as well as clinical therapy of poisoned sufferer.