Petrochemical wastewater is one of major types of industrial wastewater in China. It is of huge quantity and causes serious pollution. Wastewater contains lots of fluorescence matters. Its fluorescence spectrum could exhibit organic components and unique for each sample like fingerprint. Thus it is referred to as fluorescence fingerprint of water quality, in brief aqueous fingerprint. This paper presented that there were almost 10 peaks in the aqueous fingerprint of petrochemical wastewater from a large-scale petrochemical plant, including the peak at the excitation/emission wavelengths (λex/λem) of around 230/340 nm. That peak exists in the fluorescence spectra of various petroleum materials. The aqueous fingerprint was divided into 3 zones according to the relationship of fluorescence intensity of peaks: the linear relation between the peaks from different zones was not significant while that between the peaks from same zone was significant with coefficients of above 0.85. The zone around λex/λem=230/305 nm might relate to benzene compounds and the zone around λex/λem =220～320/230～440 nm (excluding the zone around λex/λem=230/305 nm) showed close relation with the raw materials (petroleum materials). The intensity of each peak had a fixed range. That range and relationships between peaks could be the evidences for diagnosing if the performance of the production processes is proper.