The invention discloses self-repairing concrete and a preparation method thereof. The self-repairing concrete comprises the following raw materials, in parts by weight: 200-300 parts of cement, 350-450 parts of sand, 800-1000 parts of gravel, 60-100 parts of water, 60-80 parts of sodium alginate, 35-55 parts of calcium chloride, 10-20 parts of sodium dodecyl sulfonate, 35-55 parts of hydroxymethyl cellulose, 40-60 parts of anti-cracking fibers, 10-20 parts of a silane coupling agent, 5-10 parts of a water reducing agent, 15-30 parts of calcium oxide and 20-30 parts of repair capsules; and the preparation method comprises the following steps: mixing the cement, the sand, the gravel, the sodium alginate and the hydroxymethyl cellulose under stirring, adding the sodium dodecyl sulfonate, the anti-cracking fibers and the silane coupling agent, performing mixing under stirring for 10-20 min, adding the water reducing agent and the water, performing stirring for 40-50 min, adding the calcium chloride and the calcium oxide, performing stirring for 20-30 min, finally adding the repair capsules, and performing stirring to obtain the self-repairing concrete. The self-repairing concrete provided by the invention has the advantages that the raw materials for preparing the concrete are easy to obtain, the construction is convenient, cracks of the concrete can be subjected to self repairing and the strength is higher after the cracks are repaired.