The aim of this research is to consider the Effect of Eight weeks Hydrotherapy Exercises on the Mental Health of Men staffs of Bid boland gas purge company of Omidiyeh city. The method of this research is semi-experimental type that has been done on experimental and control groups. Celburg and healer general health questionnaire GHQ-28 has been used in this study. This questionnaire has four dimensions (Physical Complaint, Anxiety, Disorder in Social adequacy, Depression).Also by using hydrotherapy exercise in the format of aerobic exercise the experimental group was practiced in swimming pool. The statistical society for the study is all the 40-50 years old male employees (n=200) in the Bid boland gas purge company that after calculating the mean of mental health scores (mean= 50.69) and also standard deviation (SD= 13.88) in statistical population, with one and half SD higher than average (50.69 + (1.5×13.88), 40 participants were selected and then these people randomly divided into 2 experimental(n=20) and control(n=20) groups. Analyzing of data was performed by computer and using spss software and statistical method of independent-sample t-test. Considering the study findings showed that hydrotherapy exercise of running in water with intensity of 60% to 70% of Maximum Heart Rate (MHR) has a positive effect on mental health and its dimension. Since level of hormones such as nor epinephrine, serotonin and dopamine is low in body of some one who is suffering than depression and anxiety. It seems that hydrotherapy exercise could increase level of these hormones. (Gaszkow,2004)suggest to person who is suffering than depression ,anxiety that for decrease depression and anxiety and another disorders do hydrotherapy exercise in swimming pool with intensity of optimal aerobic exercise that was suggested by researcher.( Netz,2005). In addition, when exercise is done in water the persons have at least pressure on their joints in compare with do exercise in out of water and also have goog feel.