The invention discloses a low-g micromechanical acceleration latching switch. The low-g micromechanical acceleration latching switch comprises an insulation substrate, a detection mass block, a plurality of anchor points, a plurality of contacts, a plurality of contact support beams, a plurality of detection mass block support beams and a plurality of overload protection structures; and the anchor points, the contacts, the contact support beams, the detection mass block support beams and the overload protection structures are symmetrically distributed relative to the X axis and the Y axis of the insulation substrate. The movable contacts of the micromechanical switch adopt hemispherical and wedge-shaped composite structures and form line contacts with side contacts, and energy loss in the motion process is reduced; the movable contacts form face contacts with the induction contacts, contact resistance values are reduced, and contact reliability is improved; the detection mass block, the flexible beams, the contacts and the anchor points are distributed in a completely axisymmetric manner, and bidirectional latching in plus or minus Y directions can be achieved; the detection mass block support beams are symmetrically distributed on two sides of the detection mass block, the structural layout is reasonable, and low-g latching is easy to achieve; and, through adjustments of gaps between the detection mass block, the flexible beams and the contacts, a latching threshold can be convenient to adjust, and the threshold scope is wide.