To assess the risks of forchlorfenuron after application, a residue analysis method for ferchlorfenuron in cucumbers and the red soil of Southern China was established, and the dissipation behavior and residue characteristics of forchlorfenuron were studied under field conditions. The field trials, including dissipation and residue experiments, were conducted in Hunan, Yunnan and Hainan Provinces. Forchlorfenuron was applied at 32 a.i.g ha-1 rate for the dissipation study and both 21 and 32 a.i.g ha-1 for the residue study. Representative cucumbers and soil samples were collected at predetermined intervals for HPLC for UV-detector analysis. The average recoveries of the method were 80.8%-92.0% with coefficients variation (CV) between 0.4% and 11.8%. The detection limit of forchlorfenuron in cucumbers and soil samples was 0.003 mg · kg-1 and the minimum detectable amount was 3.0×10-10 g. The half life of forchlorfenuron in cucumbers in the three provinces changed as: Yunnan (5.50 days), Hunan (5.88 days), and Hainan (6.53 days) and in the soil was observed: Hainan (6.54 days), Hunan (7.64 days), and Yunnan (8.39 days). The maximum terminal residue in cucumbers at 32 a.i.g ha-1 rate after 5 days was 0.009 mg · kg-1 (Yunnan) followed by 0.0085 mg · kg-1 (Hainan) and 0.0082 mg · kg-1 (Hunan) which was below MRL value of 0.01 mg · kg-1 established by the USA, EPA. So a waiting period of 5 days should be established after spaying on cucumbers to avoid hazard to human beings. To assess the risks of forchlorfenuron after application, a residue analysis method for ferchlorfenuron in cucumbers and the red soil of Southern China was established, and the dissipation behavior and residue characteristics of forchlorfenuron were studied under field conditions. The field trials, including the dissipation and residue experiments, were conducted in Hunan, Yunnan and Hainan Provinces. Forchlorfenuron was applied at 32 aig ha-1 rate for the dissipation study and both 21 and 32 aig ha-1 for the residue study. Representative cucumbers and soil samples were collected at predetermined intervals The detection limit of for chlorfenuron in cucumbers and soil samples was 0.003 mg · kg-1 for HPLC for UV-detector analysis. The average recoveries of the method were 80.8% -92.0% with coefficients variation (CV) between 0.4% and 11.8% and the minimum detectable amount was 3.0 × 10-10 g. The half life of forchlorfenuron in cucumbers in the three provinces changed as: Yunnan (5.50 days (6.54 days), Hunan (7.64 days), and Yunnan (8.39 days). The maximum terminal residue in cucumbers at 32 aig ha Which were below MRL value of 0.01 mg · kg-1 (0.0000 mg · kg-1) and 0.0082 mg · kg-1 by the USA, EPA. So a waiting period of 5 days should be established after spaying on cucumbers to avoid hazard to human beings.