TO INVESTIGATE the factors affecting irrigated wheat yield loss, compared to the attainable yield, a non systematic survey experiment was conducted in 60 fields in the city of Parsabad-Moghan, during two years 2013-2014 and 2014-2015 using Comparative Performance Analysis (CPA). Sampling of wheat fields was performed randomly from 5 different points of each farm using a square meter. All the information about management operations, soil and crop characteristics including seed bed preparation, planting date, varieties and their site preparation, seed rate, planting ways, weeds control ways, amount and timing of herbicides and fungicide use and wheat harvest time were recorded during a seasonal year using questionnaire. At the end of the seasonal year, the actual yield harvested by farmer's was recorded. Among the various parameters, planting time, spike density, the number of split application of urea, land preparation operations, farmer experience and repeated use of fungicides had significant effects on wheat yield. The results showed that the average actual yield (6431.85kg/ha) and attainable yield (8749.27kg/ha), were different with a gap of 2317.42kg per hectare. The share of each of the factors were: Wheat planting time of yield gap 18%, spike density, 29%, the split application of urea 20%, land preparation operations 4.6%, farmer experience 14.3%, repeated use of fungicides 13.4%. The improvisation cases referred above can reduced yield gap and increase yield to more than 8.7ton/ha.