The invention provides an environment-friendly indoor environment purifying agent and a preparation method thereof. The invention belongs to the technical field of environment-friendly purifiers. Thepurifying agent is prepared from, by weight, 1-3 parts of nano titanium dioxide, 5-20 parts of ethyl alcohol, 6-10 parts of traditional Chinese medicine leaching liquid, 1-3 parts of natural plant essential oil, 0.2-0.8 parts of allicin and 20-50 parts of deionized water, and the traditional Chinese medicine leaching liquid is prepared from 8-14 parts of green tea, 3-7 parts of astragalus membranaceus, 2-4 parts of folium isatidis and 2-8 parts of codonopsis. All the raw materials are pure natural raw materials, are non-toxic and have no side effects. After the finished product is sprayed indoors, formaldehyde, benzene, ammonia, sulfur, nicotine, odor and the like in the space can be decomposed in a short time, the removal rate is up to 95% or above, and the efficiency is high. The effectsof antibiosis, sterilization and inflammation diminishing are achieved. In addition, the product contains natural plant fragrance, can be prepared into purifying agents with different tastes, and isfresh and pleasant.