A proton-nuclear magnetic resonance（1H NMR ） approach was presented for the determination of paracetamol in its tablet using potassium acid phthalate as the internal standard.Effects of some experiment parameters were investigated.The optimal conditions were selected as follows: relaxation delay time（D1 ）:1 s，pulse width（P1 ）:3 μs and transient number（NS）:16.The result indicated that，under the optimal conditions，the good repeatability for the method was obtained as the peak area ratios of inner standard potassium acid phthalate to sample paracetamol were all less than 0.4%.A good linear relationship between peak area ratio and weight ratio of inner standard potassium acid phthalate（δ7.44 ） to sample paracetamol（δ6.76 ）was obtained in the paracetamol concentration range of 2-10 g/L（the concentration of internal standard was about 6 g/L ），with correlative coefficient of 1.000 0.Three batches of real paracetamol tablets from different manufactures were determined by the method with standard curve and inner standard model，and the ultraviolet spectrophotometry method used in pharmacopoeia.The results indicated that two methods had no difference.