The invention provides a method for producing a heat insulating material composed of a hydrophobic aerogel, and the method includes the steps of: (1) mixing step; (2) hydrolysis step; (3) condensation step; (4) aging step; and (5) drying step. In the method, a siloxane compound, an inorganic gel, and a halogen-free surfactant are mixed and then a sol-gel process is performed to produce the aerogel heat-insulating material without water-washing. The produced heat-insulating material has preferable strength, smooth appearance, and low shrinkage and can overcome the powder-dropping problem. By the provided method, an aerogel heat-insulating board can be produced, or an aerogel cold-resisting and heat-insulating blanket can be produced by mixing with a fiber or a foam material.