Off-flavor in cultured fish has been causing more and more attention. To learn composition and concentration of off-flavor substances in tilapia culture waters under different culture patterns, this paper monitored concentration of geosmin and 2-methylisoborneol, two main odor substances in water by using purge and trap pre-treatment with gas chromatography-mass spectrometry (P&T-GC-MS). 7 farms including one reservoir and 6 intensive culture ponds were sampled in Wenchang, Hainan province, as well as 15 farms including 3 reservoirs, 6 intensive ponds and 6 vertically-integrated ponds (pig and tilapia) in Maoming, Guangdong province in May, August and October, 2013. The results showed that 2-MIB is the main odor substance in the waters, and the concentration in water ranges from 0-65.61 μg/L, while concentration of GSM in water ranges from 0-11.77 μg/L. In the three culture patterns, the concentration of the two odor substances in reservoirs is the lowest, followed by intensive ponds, whereas the integrated ponds have the highest. There are significant differences between two culture modes (P<0.05). There is no significant difference among culture months and sites. The results indicate that different culture patterns could affect the odor components in water. Sources of odor substances from vertically-integrated ponds are more complex, which are easy to produce off-flavor.