The present invention relates to a feed additive, an antibiotic-free feed and an application of the feed. The feed additive comprises the following components in parts by mass: 0.02-0.04 part of probiotics, 0.1-0.3 part of egg powder, 0.02-0.05 part of plant essential oil, 0.50-1.00 part of an organic acidifier, 0.10-0.15 part of a compound enzyme preparation and 1.0-1.5 parts of a yeast extract. The components are cooperated together to play a synergistic role. By using the antibiotic-free feed containing the feed additive to conduct a feeding for a period of time, immunity of nursery pigs is improved. In a condition of a basic same feed intake, an average daily weight gain of the nursery pigs eating the feed containing the feed additive is obvious higher than that in a control group.