The invention discloses a two-stage launching and unfolding method of a spatial flying net. A secondary launcher pushes four auxiliary pistons through a main piston, in the initial stage, the main piston pushes the auxiliary pistons to cut off a shearing pin through mechanical contact, the main piston continues to move to allow a seal ring to lose sealing effect, high-pressure fuel gas directly acts on the auxiliary pistons, each auxiliary piston pushes the corresponding connecting rod and the mass block fixedly connected with the connecting rod, so that launching of multiple mass blocks is achieved, launching synchronism of the mass blocks is achieved, launching speed is increased by utilizing the high-pressure fuel gas, and high safety is achieved. A buffer device is disposed at the bottom of the secondary launcher to lower the large recoil generated during launching of the secondary launcher. By the method, the flying net can be drawn out regularly and orderly until the net is pulled straight, the flying net can be unfolded smoothly during spatial tasks, the problem that the flying net is prone to winding, penetration and knotting during launching and unfolding is solved, and safety and reliability are increased.