Abstract: A thermally insulating glass for ovens includes a glass substrate, a thermally insulating layer and a protective layer. The glass substrate has an inner and outer surfaces, and the inner or/and outer surfaces are coated with the thermally insulating layer made of silver. The protective layer made of silicone oil is coated on the thermally insulating layer for protecting the thermally insulating layer from being oxidized. Silver can greatly enhance thermally insulating performance and reduce heat dissipation and energy consumption. Based on the high temperature resistance, protective properties and transparency of the silicone oil layer, the protective layer prevents the thermally insulating layer from being oxidized, and the work status can be observed. The process of preparing the thermally insulating glass is simple and the cost is low.