The invention provides an essential oil feed additive for drinking water, a preparation method and use thereof. The formula of the essential oil feed additive for drinking water includes: cinnamaldehyde, thymol, carvacrol, medium chain triglyceride, and a carrier. The preparation method includes: proportioning various plant essential oil reasonably, then adding medium chain triglyceride, and carrying out high pressure homogenization to obtain an oil-in-water type essential oil energy emulsion. The efficient green plant essential oil feed additive for drinking water provided by the invention can effectively improve the feed intake of pigs, enhance health level of the body, increase piglet weight gain, provides energy for sows, and improve the production performance of sows.