In the present study, the phase transition of clinoptilolite, 16(Na, K)₆[Al₆Si₃₀O₇₂]. 20H₂O, to barium zeolites, has been investigated in the alkaline hydrothermal conditions, at the presence of the barium bearing solutions, and the high temperature. Firstly, the primary sample collected from Aftar area, west of Semnan. Secondly, powdered and examined without purification. Clinoptilolite, as a natural zeolite, transformed to edingtonite, BaAl₂Si₃O₁₀.4H₂O, and harmotome, BaAl₂Si₆O₁₆.6H₂O, as the barium zeolites, in the influence of alkaline solutions, and the hydrothermal circumstances, arranged by the hydrothermal autoclaves. Finally, the processed products evaluated by the X-Ray graphs and SEM images.