Microwave absorption of nanocomposites of strontium ferrite and zinc oxide has been investigated. M-type strontium ferrite powders synthesized by a sol-gel method were combined with different concentrations of ZnO using a new method. The samples were characterized by various experimental techniques including TGA/DTA, X-ray diffraction, transmission electron microscopy, vibrating sample magnetometer and vector network analyzer. Reflection loss of nanocomposites has been measured in two frequency ranges of 8-12 GHz (X-band) and 12-18 GHz (Ku-band). The saturation magnetization of the nanocomposites decreased with increasing concentration of ZnO, but reflection loss in the Ku frequency band is enhanced by up to 5 dB for 15 % of ZnO in the nanocomposites.