The utility model provides a safe supporting mechanism, includes bracing piece, slide rail, slider, profile of tooth fixture block, locking piece and actuating mechanism, bracing piece one end is installed in treating the supporting mechanism through the pivot, and the other end is through pivot link block, the slider cooperatees with the slide rail, along slide rail rectilinear movement, the slide rail is fixed in ground or basis, the profile of tooth fixture block is a plurality of, and in line along slide rail distribution is just with slide rail relatively fixed, the locking piece is installed on the slider, is controlled by actuating mechanism and stretches out and draws back, makes the locking piece get into or shift out the scope that cooperatees and lock with the profile of tooth fixture block. The utility model discloses an above structure makes locking piece and the profile of tooth fixture block locking slider that cooperatees, and prevent the bracing piece and the tie point of treating the supporting mechanism is close to the slide rail to this forms safe supporting mechanism, prevents to turn over board, lift platform or other activity mechanisms and because control is malfunctioning, causes the accident.