The reinforced and toughened PP／PA66 in-situ composites were prepared via an extrusion-drawing-injection molding method．The influence of PA66 weight content (cd) on the phase morphology and mechanical properties of composites together with their functional mechanisms were investigated by contrast to the normal blended materials without drawing．The results show that as cd increases from 0 to 20％

the number of PA66 fibers in-situ formed rises whereas their diameter and its dispersity decrease till cd=15％ and then enhance．Simultaneously

the number of unfibrilized PA66 particles also enlarges．The continuous increment of impact strength of composites

which is superior by 65％ to that of pure PP at cd=20％

can be attributed to the increased number of fibrils and the formation of fibrillar network．The ridigized effects of fibrils and particles on the matrix contribute to the increased Young’s modulus of composites up to a plateau level

which is higher by 36％ than that of pure PP at cd=15％．The tensile strength of composites increases till cd=15％

where its value is greater by 10％ than that of pure PP

and then drops off．This is the counterbalanced effect of the reinforced effect of the dispersed phase on the matrix and the flaw effect at the weak interfaces between two phases．