Organic ammonium salt inhibitors were synthesized using hydroxytertiary amine and epichlorohydrin as raw materials. The linear expansion rate of bentonite was used as the evaluation index to optimize the synthesis conditions of the inhibitors and screen out inhibitors with good inhibitory performance on bentonite. Using clay ball experiments, evaluate the effect of the selected inhibitors on the stability of clay. The clay ball experiments show that organic ammonium salt inhibitors have strong resistance to clay hydration and expansion. The mechanism of action of the synthesized clay swelling inhibitor was investigated using scanning electron microscopy. Research has shown that after treatment with organic ammonium salt inhibitors, clay particles significantly decrease in size and size. The inhibitors effectively bind the clay layer through electrostatic adsorption and hydrogen bonding, thereby significantly inhibiting hydration expansion.