Abstarct: This work reports a simple and sensitive on-line solid phase extraction system for preconcentration and determination of Cu (II) by flame atomic absorption spectrometry (FAAS). The method is baxsed on the on-line retention of copper at pH=5.0 with the modified poly vinyl chloride by 3-(2′-thiazolylazo)-2,6-diaminopyridine (TADAP). The retained Cu (II) eluted with 1.0 mol L-1 HCl and introduced directly to nebulizer for determination. The influence of several chemical and flow variables were optimized for the quantitative preconcentration of copper (II) and a study of interference level of various ions was also carried out. At optimized conditions, the calibration graph was obtained linear over the concentration rang of 1-100 µg L-1 for 10.0 ml sample solution (200 S preconcentration time). The relative standard deviations (n=6) at 0.0020, 0.020, 0.050 and 0.10 mg L-1 level for copper were 5.0 %, 2.0%, 1.2 % and 1.0%, respectively. The 3δ limit of detection and enrichment factor were 0.33 µg L-1 and 60, respectively. The method was applied to the determination of trace levels of Cu (II) in different real samples with satisfactory results.