The CH3NH3PbI3 (MAPbI(3)) and CH3NH3PbI3/carbon nanotube (MC) composite have been successfully synthesized by a facile in situ solution method, which are investigated as the microwave absorption materials. For the MAPbI(3) particles, the minimum reflection loss is only -4.9 dB around 16.4 GHz due to the poor relative complex permittivity. Then, the relative complex permittivity of MC composites could be adjusted by changing the mass fraction of CNTs in composite, which is a vital role for the dielectric loss. The reflection loss of MC-5 composite (MAPbI(3)/CNT, 5:1 wt%) can be improved to -35.7 dB with thickness of 1.3 mm at 13.1 GHz. When the thickness is < 3.0 mm, the microwave absorption bandwidth of MC-5 is 11.8 GHz (5.0-16.8 GHz) under the reflection loss lower than -20 dB. The quarter-wavelength (lambda/4) matching model is used to discuss the microwave absorption mechanism of MC composites. These results indicate that MC-5 composite could be used as the microwave absorption materials with strong reflection loss, lightweight and broad bandwidth.