The invention provides a method for tracking the sun by a special single axis according to time variable control and a high-temperature heat-collecting device, aiming at the defects of sealing and heat preservation difficulty of a heated medium, and the like when a biaxial omnibearing sun-tracking device is used for mid-high-temperature heat collection. In the method, projection heights on a plane being perpendicular to the ground plane or on a plane being perpendicular to the ground plane and penetrating through a meridian are calculated, and the projection height angle theta=F(phi, beta) isthe function of a solar azimuth phi and an elevating angle beta. In the high-temperature heat-collecting device implementing the method, the single axis is superposed with a heat-collecting vacuum glass tube (1) arranged on a focusing line of a trough-type parabolic cylindrical heat collector (3) and is stationary through a bracket (2); the arrangement direction of the single axis varies with a projection surface perpendicular to or penetrating through the meridian; and the trough-type heat collector is driven by a driver (5) through a segment gear (4) to rotate around the single axis and track the theta angle so as to realize linear-focusing and high-temperature heat collection. The tracking device is particularly suitable for the heat-collecting equipment of a trough-type large-scale solar thermal power system.