The invention discloses a shear type quasi zero rigidity vibration isolator and a work method thereof. The shear type quasi zero rigidity vibration isolator comprises a supporting base, a positive-rigidity module, a negative-rigidity module and a supporting plate. The positive-rigidity module comprises at least one positive-rigidity unit. The negative-rigidity module comprises a first upper support, a second upper support, a first connecting rod, a second connecting rod, a third connecting rod, a fourth connecting rod, a fifth connecting rod, a sixth connecting rod, a seventh connecting rod, an eighth connecting rod, a first lower support, a second lower support, a first horizontal connecting shaft, a second horizontal connecting shaft and at least one horizontal spring. For the defects that an existing linear vibration isolator can difficultly isolate low-frequency vibration and an existing quasi zero rigidity vibration isolator is complex in structure and short in effective stroke, the shear type quasi zero rigidity vibration isolator has high static rigidity and low dynamic stiffness based on the positive and negative rigidity parallel principle, can isolate low-frequency or ultra-low-frequency vibration and is easy to machine and achieve, high in bearing capability and high in reliability.