A field experiment was carried out during winter season of 2019 at Al-Muradiya research state, Babylon government, Iraq, to study the role of the sprayed types of potassium fertilizer in improving of flag leaf contribution in grain yield of wheat. The layout of the experiment was randomized complete block design in factorial arrangement at three replicates. The experiment included spraying common and nano potassium fertilizer at booting stage, in addition to control treatment (spraying of distilled water) as a first factor, and removal treatments (removal of flag leaf at 10% anthesis stage and nonremoval) as a second factor. The results showed that the spraying of nano potassium fertilizer was significantly superior in the dry matter transporting (2.492 g), grain weight (47.80 g) and grain yield (4.855 ton ha-1). Also, the removal of flag leaf was significantly reduce of dry matter transporting (9.16%), grain weight (5.28%) and grain yield (10.84%) compared with nonremoval of flag leaf treatment which gave the highest means of these traits. The spraying of nano common potassium with nonremoval of flag leaf led to an increasing the contribution of the flag leaf in grain yield at 39 and 24% respectively compared with spraying of distilled water with removal of flag leaf, while the spraying of distilled water with non-removal of flag leaf gave 12% compared with spraying of distilled water with removal of flag leaf. Also, the contribution of flag leaf in grain yield was increased at 20% when spraying of nano potassium without removal of flag leaf compared with spraying of nano potassium with removal of flag leaf, whereas, the contribution of flag leaf in grain yield was 5.0% when spraying of common potassium without removal of flag leaf compared with spraying of common potassium with removal of flag leaf. We can conclude that spraying the nano potassium fertilizer has improved the contribution of the flag leaf in grain yield of wheat as a result to its role in stimulating thetransfer of dry matter to the reproductive parts and improving of sink capacity.