The invention provides a jaw adjustable neck guard which comprises a bracket group, a neck set group, an adjustment group and a headrest group.The bracket group includes two connectors at both ends, a bracket between the two ends and two connectors between each connector and bracket respectively.The neck sleeve group comprises a base which is connected with each connecting piece, two sliding holes which pass through the base and are adjacent to each joint end respectively, and a cover body which is closed to the base.The adjustment group consists of two slides at both ends of the adjustment group, a guide strip connected with each slide and a positioning component penetrated by the guide strip.The two ends of the head restraint group are respectively connected with the two ends of the neck sleeve group.By adjusting the group, the jaw height of the adjustable neck guard can be adjusted, and the neck length of different users can be adjusted.本創作提供一種下顎可調式護頸圈包含一托架組、一頸套組、一調整組及一頭枕組。托架組包含設於兩端的兩連接件、一設於兩端間的托部及分別設於各連接件與托部間的兩連動件。頸套組包含一與各連接件相連的底座、穿設底座且分別鄰近各接合端的兩滑孔及一蓋合於底座的蓋體。調整組包含兩設於調整組兩端的滑片、一與各滑片相連接的導引條及一被導引條穿設的定位組件。頭枕組兩端分別與頸套組兩端相連。本創作藉由調整組，以調整可調式護頸圈下顎高度，並能符合不同使用者的頸長。
