The invention discloses a lifesaving device, comprising a guide belt, a housing, a speed measuring mechanism and a speed reducing mechanism; the housing is sheathed on the guide belt; the speed measuring mechanism and the speed reducing mechanism are installed on the housing; the speed measuring mechanism comprises a speed measuring gear and a rubbed housing contacted with the guide belt in rolling manner; the speed reducing mechanism comprises a speed reducing housing having a gradually changed friction factor with the guide belt during the rotating process and a speed reducing gear for driving the speed reducing housing to rotate; the speed measuring gear is engaged with the speed reducing gear; a centrifugal speed measuring device which can be connected with the rubbed housing and speed measuring gear to drive the speed measuring gear to rotate is installed on the rubbed housing when the rotation speed of the rubbed housing reaches a pre-set value. The lifesaving device can effectively control the descending speed of the heavy article to prevent the heavy article from being descended fast. The lifesaving device is suitable for saving life on high buildings, and is capable of preventing people from being descended fast; and the lifesaving device with simple and compact structure takes small space and does not need to assemble.