Abstarct: Molybdenite is a valuable byproduct in porphyry copper flotation process whose recovery is well considerd due to its high economic value. The most important objectives of this research is to identify the cause of low recovery in the copper-molybdenum flotation circuit and also provide the strategies to icrease molybdenum grade and recovery while fixing the copper grade and recovery. In this study, factors and effective processes in order to optimize grade and recovery of molybdenum in rougher, cleaner and scavenger of Sungun copper processing plant were studied. For this purpose, same samples were taken from the entire circuit to investigate the mineralogical and mextallurgical situation. Then is laboratory studies, the effect of factors such mineralogy, grinding rate, solid percent, reagents doses, pH in rougher stage and cleaning water rate, air rate and froth height in cleaner stage and flotation process type in scavenger were investigated. Thr results showed that the most molybdenum wasting was happened in rougher tailings by 44.3%. Operational parameters for optimization of molybdenum grade and recovery in this stage were determined as feed size (-95 µm), solid percent (25), kerosene (25 g/t), pH (10.5), collector doses (31 g/t) and frothers doses (12 g/t). in optimum conditions, the grade and recovery were 8.22 and 90.8% respectively for copper and 890 ppm and 71.2% for molybdenum which showed 4% and 18% increase respectively for molybdenum recovery and grade respect to the present conditions of the plant. The results of optimizing the cleaner stage showed that increasing water and air rate, couses the decreasing molybdenum grade and also increasing water rate and froth height couses increase in copper grade. The results of optimizing scavenger stage showed that increasing stirring (600-1000 rpm) molybdenum grade in concentrate reach 8823 ppm with 90% recovery, which show 0.32% improvement respect to the present conditions of plant. Another approach for prevent of wasting molybdenum to the tailing was depressing molybdenum in scavenger stage by adding dextrin. In this case, molybdenum grade in scavenger tailing was increased from 234 to 1471 ppm by adding 600 g/t dextrin, then performing a molybdenum flotation process on scavenger tailing a concentrate with 6906 ppm molybdenum grade was obtained mixing the produced concentrate with the final concentratewill prevent for molybdenum wasting and increases 2.3 times in molybdenum content in final product respect to the present condition at the plant.