【Background】As an alien species, Tilapia sp.is widely distributed in South China, yet a detailed description on the distribution and abundance in natural waters is lacking. 【Method】We surveyed tilapias in the main rivers of Guangdong Province, inlcuding the Pearl River tributary (Xijiang River, Beijiang River, Dongjiang River), Hanjiang River, Jianjiang River and Tanjiang River, in order to clarify the distribution and the invasion situation. We collected data on the age structure, sex ratio, sex development, and feeding habits. 【Result】Tilapia was found in the major rivers of Guangdong Province and it has a stable, self-sustaining populations. The Jianjiang River has the largest number, accounting for approximately 60% of the total fisheries catch by weight. The Xijiang and Beijiang Rivers have smaller numbers and contributes <1% by weight. In these rivers, many 2 y old individuals and mature individuals were found in each population and a large number of juveniles were also collected. 【Conclusion and significance】Tilapia has established natural populations in the major rivers in Guangdong Province because it has been able to overwinter and reproduce in natural waters.