The group composition of crude oil was analyzed by on-line coupled capillary HPLC-HTGC. After removal of asphaltenes, the oil sample was separated by capillary HPLC into aliphatics, aromatics and resins. The interface cut and stored each fraction, and transfered them into GC sequentially. The group contents of oil were determined by FID. The error of reproducibility(RSD) was less than 3%. The method is accurate, time saving, and easy for operation. It is very important for quality control and development of new and better products in crude oil.