In recent years, the undesirable quality of irrigation water has a profound effect on the growth and production of pistachios. These studies were conducted to investigate the effect of important irrigation water qualitative parameters and classification of them on pistachio yield. For this purpose, 53 water sources were selected with a variety of quality in pistachio orchards. Sampling and complete analysis were done for each source water sample. For all the gardens, management questionnaires were prepared. Step-by-step multi-variable regression analysis shows that the EC, SAR and B of water, were more effective on pistachio yield, respectively. The correlation coefficient (R2) of the relationship between the yield and water salinity, SAR and B was about 0.82, 0.81 and 0.67 respectively. The qualitative characteristics of irrigation water quality were ranked in suitable classes (S1, S2, and S3) and unsuitable (N). Excessive threshold increases of these characteristics have a decreasing effect about 65% on yield of the studied orchards. The statistical analysis shows that the average of water salinity is 11 dS. m-1, SAR is about 20.1 and B is 6.9 mg.l-1. Due to the negative effects of irrigation water quality on pistachio yield, to achieve optimal use, special management practices is necessary, and a new classification for irrigation water based on the proposed table is recommended in pistachio orchids.