Vacuum heat collecting pipe

The invention relates to a vacuum heat collecting pipe which is mainly used for the field of groove-type solar medium-high temperature heat utilization. The vacuum heat collecting pipe comprises a glass outer pipe (2) and a coaxial metal inner pipe (1); the glass outer pipe (2) sleeves the metal inner pipe (1); the middle of the glass outer pipe (2) is thick and the glass outer pipe (2) is gradually thinned towards both ends; each of both the ends of the glass outer pipe (2) is in sealing connection with one kovar alloy ring (3); each kovar alloy ring (3) is connected with a bellows (4); and two bellows (4) are respectively connected with both ends of the metal inner pipe (1). The invention can well solve the problem that in the operating process of a medium-high temperature heat collecting pipe, due to nonuniform heating, the metal inner pipe is deformed to break the glass outer pipe.