Abstarct: This study was aimed at estimating the wheat yield gap in sex regions of Golestan province, using modeling by SMM-Wheat model. The regions were Atrak, Aghabad, Sultan Ali, Imer, Kaka, and Fajr. The required data included weather information, soil properties, amount of observing pest and weed control, irrigation, and fertilization principles by farmers. The results indicated that the irrigated-wheat yield grain increases by 19.235 kg/ha for a one percent increase in observing pest and weed control by farmers. Also, the wheat yield grain increases by 39.669 kg/ha for a one percent increase in observing appropriate fertilization principles by farmers. In terms of yield gap under rainfed conditions, the regions ranked from higher to lower as Sultan Ali, Fajr, Atrak, Imer, Kaka, and Aghabad. In terms of yield gap under irrigated conditions, the regions ranked from higher to lower as Kaka, Sultan Ali, Imer, Fajr, Atrak, and Aghabad. Under rainfed and irrigated conditions, the wheat yield gap decreased by 116.6 and 172.75 kg/ha, respectively for a one percent increase in observing appropriate fertilization principles by farmers.