The invention discloses a control method of a foldable arm rest. The control method includes a detection step: detecting whether each arm section is in a completely
closed state or not, a calculation step: ensuring that the arm section is in a completely folding state when the arm section is not in a completely
closed state, obtaining the folding state of each arm section, working out the maximum distance L between the arm rest portion which is between the predetermined arm section and the
tail end of the folding arm rest and a
hinge point of the root end of the predetermined arm section according to the folding state of each arm section, and working out the allowable maximum
angular velocity w when the predetermined arm section moves according to a predetermined linear velocity V and the maximum distance L, and a control step: controlling an actuating part which drives the predetermined arm section, and enabling the predetermined arm section to move at an
angular velocity which is less than or equal to the maximum
angular velocity w. The invention correspondingly discloses a
control system of the foldable arm rest and
engineering machinery. The control method and the
control system has the advantages of being capable of improving folding speed of the foldable arm rest and working efficiency, easy to control, low in cost and good in stability.