Abstract: A novel dual-koch fractal antenna with sleeves is presented, and dependences of its resonant parameters on the indentation angles, the half cone angles, the sleeve space and the sleeve height are investigated by using the method of moment. Based on these discussions, a double-band unipole antenna for application of GSM/DCS is designed by using the genetic algorithm. All the analyses show that dual-Koch fractal antenna has much lower resonant frequency than single-koch fractal antenna, and the resonant frequency decreases with increase of the indentation angle. The sleeves can effectively improve the performance of the fractal antenna at high resonant frequency. That is, its space and its height have excellent ability to tune at high resonant frequency.