Background: Recent years have seen an unusually large number of patients undergoing posterior spine operations. Studies have recorded blood loss between 1 and 3 liters for posterior spine procedures. Drugs used to control hypertension must meet a set of criteria that include being easy to administer and its effect quickly disappears when administration is ceased. Also have a rapid elimination without toxic metabolites and minimal influence on vital organs and have predictable dose-dependent effects. Objectives: The aim of this study is comparing the effect of magnesium sulphate and Dexmedetomidine during spine surgeries in decreasing the surgical bleeding and controlling blood pressure. Patients and methods: There were sixty participants in this randomised prospective research of spine surgery patients. Thirty patients were assigned to Group M, which was given magnesium sulphate. While thirty patients were assigned to Group D, where they were given dexmedetomidine. Results: Both groups had comparable surgical data, except for the duration of operation, which was significantly shorter in group D (1.92±0.27) than in group M (2.20±0.19) p-value <0.001. The Systolic blood pressure (SBP) was statistically significantly higher in group M than group D at induction, A5, A15 and A30 (p-value =0.001, 0.001, 0.001, 0.006). After 30 minutes of induction (A30), the diastolic blood pressure (DBP) in group M (61.07±3.12mmHg) was statistically significantly higher than in group D (59.1±2.25mmHg) p-value = 0.022. In addition the group D was significantly less in blood loss (366±50.1 ml) than in the group M (394.5±35.2 ml) p-value = 0.005. Conclusion: Dexmedetomidine provides better surgical field, controlled hypotension, and less analgesia than magnesium. But consider a long recovery duration.