Objective To investigate the situation and trend of drugs added illegally into weight-losing foods in our country. Method Fifteen chemical drugs in 377 samples collected from the national surveillance works on health-related products in 2005–2008 were detected by UPLC-Ms/Ms (Ultra Performance Liquid Chromatography–Mass Spectrometry). Results The detection rate of illegal drugs in all samples was 33.4%, and was decreased from 2005 to 2008. The detection rate of illegal drugs in capsule samples （57.8%）was higher than other forms. The detection rate of sibutramine was decreasing while that of phenolphthalein was increasing. The samples in combining use of drugs accounted for 41.7% of total positive samples in 2008. Conclusion The situation of using illegal drugs in weight-losing foods was still very serious in the whole country. Much more attention should be paid by food hygiene supervision departments on combined drugs used in weight-losing products.