The invention discloses an air purifying agent and a preparation method thereof. The preparation method comprises the following steps: mixing zeolite, diatomite, nano- titanium dioxide, active carbon, sodium percarbonate and a dispersant to obtain mixed powder M; adding water into the mixed powder M and mixing and granulating to obtain the air purifying agent. The problems that a common air purifying agent has a relatively low adsorption rate on harmful substances and particularly has a relatively low absorption rate on substances including hydrogen sulfide, ammonia and the like, the service life is short and the function is single are solved.