Abstract: A novel perfect metamaterial absorber(PMA) is proposed based on square-patch absorber by Minkowski fraction and slot, and the mechanism of absorber is analyzed . The new perfect metamaterial absorber is loaded on microstrip antenna in order to reduce antenna's in-band RCS. The simulated result shows that the operating frequency is reduced by 8. 6% and the absorbance reaches 99. 97%. The antenna performance has not been influenced, while the in-band RCS of the antenna has declined effectively. There is a good agreement between measured and simulated results showing that this material can be used for microstrip antenna's in-band stealth