We report a high-power self-frequency-doubled (SFD) Yb:YCa4O(BO3)3 laser by employing a simple and high-integration monolithic configuration with an oscillator length of 6 mm. By reducing the reabsorption and increasing the quantum efficiency, the continuous-wave output power of 21.6 W was obtained with an optical conversion efficiency of 19.0% at the wavelength of about 510 nm. To our knowledge, the results represent the highest output power of a SFD laser. We believe that the high-power SFD laser with a highly compact structure will have broad and promising application prospects in laser display, medical treatment, spectral analysis, scientific research, and other fields.