In this paper, Quantitative real-time reverse transcription-polymerase chain reaction (qRT-PCR) was used to study the tissue-specific changes of mRNA expression by salinity in case of the hybrid×Sarotherodon melanotheron(). As a new variety ,“GILI” tilapia characterized by high salt tolerance and fast growth is suitable for marine culture. The present results showed that: gene expressed in all tested tissues of gill, liver, kidney and intestine under salinity below 25. When the salinity increased from 0 to 48, the mRNA expression level showed a positive correlation with salinity in gill (). When the salinity raised to 64, the mRNA expression level reached the highest peak after 3 h in gill and intestine, and after 5 h, and there were significant differences between 1 h and 3 h, and between 3 h and 5 h (<0.05). In liver, the maximum level appeared in 5 In kidney, the expression levels descended continually with the increase of exposure time, but no significant differences were detected in different time) Above results revealed that, in the “GILI” fish which acclimates to environmental salinity over 25, it is primarily the gill chloride cells to secrete the cation ions and to maintain water and salt balance. So, it could be considered that gill plays a leading role in osmoregulation of “GILI” tilapia. gene in euryhaline teleosts in fresh, saline and hypersaline water.