A passenger boarding bridge leveling mechanism configured to be mounted on a passenger boarding bridge , wherein the passenger boarding bridge leveling mechanism comprises: a four-bar linkage mechanism comprising a mounting base and three bars, in which the mounting base may be fixedly mounted on the passenger boarding bridge ; in which one of the three bars extends outwards, and a leveling wheel and a first detection switch are mounted at an end of the outwardly extending bar, the first detection switch being used for detecting a vertical displacement of the leveling wheel on an aircraft fuselage ; a preload apparatus , an end of the preload apparatus is connected to the mounting base , and the other end of the preload apparatus is connected to one of the three bars, the preload apparatus has a preload to make the outwardly extending bar maintain a tendency of extending outwards, characterized in that the three bars of the four-bar linkage mechanism comprise: a driving bar , a lower portion of which is hinged to the mounting base ; a driven bar , a lower end of which is hinged to the mounting base , the driven bar being located above the driving bar ; a mounting bar , one end of which is hinged to an upper end of the driven bar , the other end of which extends outwards and is mounted with the leveling wheel and the first detection switch; an upper end of the driving bar being hinged to the mounting bar. bridge , wherein the passenger boarding bridge leveling mechanism comprises: a four-bar linkage mechanism comprising a mounting base and three bars, in which the mounting base may be fixedly mounted on the passenger boarding bridge ; in which one of the three bars extends outwards, and a leveling wheel and a first detection switch are mounted at an end of the outwardly extending bar, the first detection switch being used for detecting a vertical displacement of the leveling wheel on an aircraft fuselage ; a preload apparatus , an end of the preload apparatus is connected to the mounting base , and the other end of the preload apparatus is connected to one of the three bars, the preload apparatus has a preload to make the outwardly extending bar maintain a tendency of extending outwards, characterized in that the three bars of the four-bar linkage mechanism comprise: a driving bar , a lower portion of which is hinged to the mounting base ; a driven bar , a lower end of which is hinged to the mounting base , the driven bar being located above the driving bar ; a mounting bar , one end of which is hinged to an upper end of the driven bar , the other end of which extends outwards and is mounted with the leveling wheel and the first detection switch; an upper end of the driving bar being hinged to the mounting bar. a driving bar , a lower portion of which is hinged to the mounting base ; a driven bar , a lower end of which is hinged to the mounting base , the driven bar being located above the driving bar ; a mounting bar , one end of which is hinged to an upper end of the driven bar , the other end of which extends outwards and is mounted with the leveling wheel and the first detection switch; an upper end of the driving bar being hinged to the mounting bar. <EOS>