The invention belongs to the field of indoor decoration coatings, and relates to a flexible ecological environment-friendly diatom ooze coating and a preparation method thereof. The diatom ooze coating is prepared from diatomite, flexible fibers, a microcapsule expanding agent, a modifier, a flexibilizer, flexible graphite, talcum powder, an inorganic bonding agent and inorganic pigments. According to the flexible ecological environment-friendly diatom ooze coating, the diatomite is taken as a main raw material to be composited and added with the flexible fibers and the microcapsule expanding agent, the surface of the diatomite is coated with the flexible fibers with a network structure through modifying and mixing, therefore, the flexibility and the strength of the diatomite are improved, and the phenomenon that the diatom ooze is cracked and falls off in the using process is avoided; meanwhile, by mixing the flexibilizer with the flexible graphite, the strength and the anti-crack property of the diatom ooze are further enhanced, the technical problems that a diatom ooze coating is prone to fall off and crack and low in strength are solved, and the comprehensive properties of a diatom ooze wall material are improved. The obtained diatom ooze coating has the advantages of not falling off, not fading and not cracking to fall off and is simple in preparation process, low in cost and easy to popularize.