The invention discloses a salt-tolerant rubber plug compounded for real-time use and a preparation method thereof. The rubber plug is composed of a phenolic aldehyde system, a catalyst system, a copolymer solution system and a saline water system, the phenolic aldehyde system is composed of phenol, resorcinol and formaldehyde solution, the catalyst system is composed of sodium hydroxide, triethanolamine and distilled water, the copolymer solution system is composed of acrylamide/2-acrylamide-2-methylpropane sulfonic acid copolymer and sodium chloride solution, the saline water system is a mixed solution of sodium chloride and calcium chloride, and mineralization degree of the mixed solution is not higher than 250000mg/L. the salt-tolerant rubber plug has the advantages that (1) the systemsare packed separately, the phenolic aldehyde system can be stored at room temperatures for a long time, the rubber plug can be compounded for real-time use and is convenient to use, and unnecessary wastes are avoided; (2) salt tolerance and strength of the rubber plug are improved.