In this paper, photorefractive (PR) crystals of Cu and Mn- doped (K0.5Na0.5)0.2(Sr0.75Ba0.25)0.9Nb2O6 were symmetrically studied. We reported the growth conditions, the absorption properties and the photorefractive properties including two wave mixing (TWM) and self-pumped phase conjugation (SPPC). The mechanism of Cu-doped KNSBN was referred briefly, and the influence of the different sites occupied by doping ions on PR properties was also discussed. All these results reveal that: (1) In Cu-doped KNSBN crystals, the photorefractive properties become better with the increase of the doping level, such as higher effective charge carrier density, larger coupling coefficient, faster response rate, higher SPPC reflectivity. (2) The thinner sample shows larger coupling gain coefficient, which is due to the light creep effect and beam fanning effect. The response time becomes shorter with the decrease of the thickness. (3) In Cu:KNSBN crystals, the coupling gain coefficient of TWM was obtained up to 35 cm-1. (4) In Cu:KNSBN and Mn:KNSBN samples, the SPPC reflectivity up to 73% have been obtained, respectively. (5) The C-site in the tungsten-bronze structure of KNSBN has an effect on the PR properties of the crystal. All these results show that doping in KNSBN is an effective method to improve the PR properties. The Cu-doped KNSBN crystal is a very promising photorefractive material.