Estimation of reference CROP potential EVAPOTRANSPIRATION (ETo) is essential in many irrigation projects. Also, concerning the deficit of water reresources in Iran, ETo prediction through using time series has paramount role in future programming. Based on this, monthly ETo values were calculated using monthly weather data up to year 1388 of synoptic stations in Fars province containing Abadeh, Eghlid, Darab, Zarghan, Dorodzan Dam, Shiraz, Fasa and Lar. Then, in each station it was assumed that about 20 percent of last ETo values were not available, and consequently these values were predicted using time series model of SARIMA, and then the predicted and calculated values of ETo in each station were compared with line one: one, separately. The results showed that the same time series model were not appropriate for all stations. Moreover, the results indicated that there were not significant diferences between the predicted and calculated values of ETo in each stations. Therefore, ETo values were predicted up to year 1403 for each station, separately. The results generally indicated an increasing trend in ETo prediction in Fars province.