Background and Objectives: The open pit miners in tropical region suffer from severe heat stress especially during summer. The aim of this study was to evaluate heat stress based on heat strain score (HSSI) index and its relationship with physiological parameters of an open pit miners. Materials and Methods: This descriptive study was conducted on 120 healthy and acclimatized miners. Tympanic and skin temperatures were measured using a Using a thermometer (model FT-70) manufactured by Beurer Co, Germany. Heart rate and blood pressure were monitored by digital instrumentation (Emsig BO26 model) digital instrumentation. All environmental and physiological parameters were simultaneously measured and recorded. HSSI questionnaire was also completed. Finally, linear regression and Pearson's correlations were determined. Results: According to HSSI more than 6.7 percent of workers had any thermal strain, 50 percent of workers may experience thermal strain and 43.3 percent suffered from heat strain. A significant correlation between studied physiological parameters, including the tympanic temperature, skin temperature, heart rate, systolic and diastolic and HSSI were indicated (p<0.01). The highest correlation coefficient was observed for heart rate (r=0.450). Although a significant correlation was found between the HSSI index and physiological parameters, the values were low. Conclusion: The workers in open pit miners were exposed at risk of heat strain hazards and the highest score of heat strain index was in drilling unit. It seems can used of heat Strain Score Index for evaluating of heat strain in such workplaces. How to cite this article: Jafari MJ, Teimori GH, Khodakarim S, Assilian-Mahabadi H. Investigation the Relationship between Heat Strain Score Index and Physiological Parameters among Open Pit Miners. J Saf Promot Inj Prev.2016; 3(4):213-22.