The invention relates to the technical field of ammonium ion sieve forming and especially relates to a method and a device for coagulating-bath pelletizing forming of an ammonium ion sieve with adjustable particle size. The method is characterized by comprising the following steps: dissolving a macromolecule binder into an organic solvent to form a bonding solution; adding ammonium ion sieve powder into the bonding solution, and continuously stirring and mixing, thereby forming a pelletizing solution; preparing the pelletizing solution into ammonium ion sieve grains in the manner of coagulating bath under a stirring condition. The method has the beneficial effects that compared with traditional ion sieve and molecular sieve forming, the method takes coagulating-bath forming rather than high-temperature sinter forming as a forming principle, so that heat energy is saved, and the ammonium ion sieve can be formed at normal temperature; the grain size is adjustable, so that the whole pelletizing process is simple and convenient. The device for coagulating-bath pelletizing forming of the ammonium ion sieve with adjustable particle size integrates various functions of stirring and mixing, controlling the dripping speed and forming the granular ammonium ion sieve; due to the modularized design, the stirring, the dripping and the forming are integrated with each other; a simple and efficient pelletizing mode can be realized; the device is a convenient granular ammonium ion sieve forming device.