This study concerns on investigation of diffusion mechanism of polymer composite reinforced by waste bio-fibers from chicken fiber in different kinds of water such as (Dead Sea water, river water and distilled water). The prepared samples were immersed in water mentioned above for equal time at room temperature and it was measured by weight before and after immersion. The values of diffusion coefficient (D) are evaluated for each type of water. It was found that the distilled water has higher value of (D) (low absorption resistant) ( 41.28* 10 -13 m2/s , 44.67 x 10-13 m2/s), it is followed by the river water (15.54 10 -13 m2/s , 21.18 10 -13 m2/s) then dead sea water (low absorption resistant) (6.34 * 10 -13 m2/s , 6.05 * 10 -13 m2/s) of treated and untreated sample with alkaline solution (NaOH)