The invention discloses a diaper rash-proofing coating agent, which comprises the following components in parts by weight: 10-15 parts of polyethylene glycol, 5-10 parts of aloe powder, 5-10 parts ofbisabolol, 5-10 parts of farnesol, 5-10 parts of geranium essential oil, 5-10 parts of tea tree essential oil, 5-10 parts of phytosterol, 0.2-0.5 part of carboxymethyl chitsan, 5-10 parts of softeningagent, 8-16 parts of emulgator, and 25-35 parts of water. The invention further discloses a preparation method of the diaper rash-proofing coating agent. By using the preparation method of the diaperrash-proofing coating agent, the obtained diaper rash-proofing coating agent is helpful to preventing the attack of diaper rash of babies and infants, the old and the patients, and is good in effectand strong in practicability after being coated on the surface of diapers.