Abstract: Targeting at the problem of compressing of fabric resulting from closing of the mold in RTM,the changes in thickness and fiber volume fraction of plain-woven fabrics when compressed were studied along with compressing parameters and a series of cross-section images of composites at various degrees of compressing were captured under a microscope with a CCD camera.It was found that the wet or dry state of the fabric and compressing times have significant influence on its compressibility.The initial fabric bulk compressibility reduces with increasing compressing times while relaxation takes place after removing the load.In addition,the voids between the fiber and resin-rich areas decrease with increasing compressing load as observed from the microstructure image in which the yarn waveform and cross-section have deformed under compression.