The invention discloses a passive suspension vibration isolation method and device with zero stiffness characteristics, and relates to the fields of gravity environment ground simulation, low-frequency vibration isolation, ultralow-frequency vibration isolation and the like. The passive suspension vibration isolation method and device with the zero stiffness characteristics are put forward to meetincreasingly higher requirements for space gravity ground simulation experiments in aerospace engineering, and to solve the existing technical problems in the low-frequency and ultralow-frequency vibration isolation. According to the suspension vibration isolation device, based on geometric nonlinear negative stiffness characteristics and the adjustability of geometrical parameters thereof, a vertical elastic element, sliding rails, sliding blocks, horizontal elastic elements and connecting rods are connected to a load, the characteristic of accurate zero-inherent frequency in a design rangeof the device is realized through parameter configuration, and a constant force that is collinear with the direction of gravity of the load and has no relation with displacement of the load can be provided for the load. The resultant force acting on the load in the design range is fixed in value, so that the load is enabled to be in a certain specific gravity environment. The full-frequency-band immunity of the load to the vibration environment is realized, and ultralow-frequency vibration isolation, the zero-rigidity suspension of a modal test and the ground simulation of the spatial gravityenvironment are realized.