Abstract: A UPLC-MS/MS method was established for qualitative detection and quantitative determination of mepiquat chloride in the bio-samples.A poisoned dead rat model was established by intragastric administration of 1/2LD₅₀ mepiquat chloride(200 mg/kg).Then the rats would be dissected at 3rd ,8th ,and 12th hour to collect the rats′ specimen(heart,liver,spleen,lung,kidney,brain,muscle,small intestine,stomach),and analyzed by UPLC-MS/MS immediately.After ig administration in the rats,small intestine ,stomach,bladder,kidney were the main distribution organs within 12 hours with low levels in the lungs and the highest level in the small intestine.The concentration of these visceras changed little within 8 hours,but had a sharp decline after 8 hours .Each viscera had significant difference in contrast to the brain(P<0.05).It was found that there was a postmortem maldistribution of mepiquat chloride in these rat models and the concentration of visceras changed over time.The poisoned dead rat model,the UPLC-MS/MS method and the postmortem distribution of mepiquat chloride can be applied to the forensic identification and help taking samples for toxicology analysis.