A wireless transmission system capable of automatically adjusting transmission power includes a main wireless apparatus and plural secondary wireless apparatuses, and the main wireless apparatus is capable of detecting the data rate between the secondary wireless apparatuses, and increasing or decreasing the transmission power of any one of the secondary wireless apparatuses by a master controller, or increasing or decreasing the transmission power of the main wireless apparatus, so that the data rate and/or transmitting distance between the main wireless apparatus and the secondary wireless apparatuses can be optimized.