The molecular structure of 5-［2-propoxy-5-（3,5-dimethylpiperazin-1-yl-sulfonyl）phenyl］-1- methyl-3- n-propyl-1,6-dihydro-7H-pyrazol［4,3-d］pyrimidin-7-one was elucidated by 1D NMR（1H,13C NMR） and 2D NMR techniques，including gradient homonuclear correlation spectroscopy（1H-1H COSY）,gradient heteronuclear single-quantum coherence（HSQC） and gradient heteronuclear multiple-bone coherence（HMBC）,together with the infrared spectral analysis and elementary analysis.The 1H NMR and 13C NMR signals for 5-［2- propoxy-5-（3,5- dimethyl- piperazin-1- yl-sulfonyl）phenyl-1-methyl-3-n-propyl-1,6-dihydro-7H-pyrazol［4,3-d］pyrimidine-7-one were assigned.The data obtained could be used to detect sildenafil analogues.