This research deals with study of Rheological behavior of polypropylene (PP) blended with different percentages of waste pre-injection (runner) to achieve the same characteristics required for the production of medical syringes (cylinder part ). Injection machine used to produce this part operates at melt flow rate (MFR) between (22-28) g/10 min in syringes factory of Babylon city. PP provided from(HYSONG )Korean company with grad resin J801. X.R.D test is used to measure the level of crystalline and contamination in PP.10 %,20%,30%,40%and 50% of the runner mixed with PP to measure the (MFR), swelling ratio(diameter of extrudate/diameter of die), and density of each blend at three different temperatures 233 °C,230°Cand 227 °C, three different loads 2.16kg,3.80kg and 1.965 kg. and two size of runner pellet ( large and small) .The Instrument (ISO 1133:2005) is used to measure MFR, liquid density mode of GP-120S device used to measure the density. The XRD test shows that the blends and runner have higher contaminations and lower crystallization level than that in virgin PP. The results of first size showed that the MFR values increase and density decreases with the runner percentage, temperature and load increasing. The swelling ratio increases with the runner percentage and load increasing while decrease with the temperature increasing .For the second size the MFR , density, and swelling ratio behave in the same manner of the first size ,but with lower quantities due to the reduction in pellet size. This increases the flexibility to adding more runner to the blend and keeping the MFR within the acceptable range.