Grape (Vitis vinifera L.) has a special position among horticultural products consumers because of high diversity, distribution, level of culture and the multiple uses. To achieve this goal, use of compatible varieties with different environmental conditions and high production, optimal consume of fertilizers and pesticides with minimal adverse environmental effects, are very good solutions. Traditionally, phosphates (Pi, salts of phosphoric acid, H3PO4) have been used for plant fertilization, and phosphites (Phi, salts of phosphorous acid, H3PO3) have been used as fungicides. Potassium is one of the most important elements that needed for growth and increase the quantity and quality of grape fruit. Vineyards with high production, more nitrogen and water deficit is seen potassium deficiency in leaf, cluster and berry. In most vineyards, an application of complete fertilizer in growth begin lead to more vegetative growth and reduce plant tolerance to biotic and abiotic stresses and also is not able to supply of vines needs to high potassium. This experiment was arranged in factorial design included 3 cultivars (Askari, Sefidali and Razeghi) and 3 concentrations of potassium phosphite (0, 1500 and 3000 mg/Lit) based on completely randomized design and 3 replications in field conditions was sprayed after 50% anthesis in inflorescence. Some of the important fruit quantitative traits and yield components of grape were measured. The results of variance analysis showed that there were significant differences for all or some of the fruit characteristics and yield components between Askari, Sefidali, Razeghi cultivars, 3 concentrations of potassium phosphite and their interactions. Sefidali cultivar, potassium phosphite with 3000 mg/Lit and their interaction were superior and better than other treatments. In traits of the numbers of opened flowers per cluster (510.64 flowers), berry per cluster (139.22 berries) and cluster per shrub (27.62 clusters). Also Askari cultivar and
