The invention discloses a method for preparing in-situ three-dimensional continuously-reinforced Al-base composite material. The method includes the steps of mixing Ti powder, Al powder and graphite powder according to the mole ratio of 2 to 1-1.2 to 1, grinding the powder and obtaining mixed powder; placing the mixed powder into a mold, carrying out cold-pressing and obtaining green bodies; and finally adding the preheated green bodies into molten Al with the temperature being 700-900 DEG C, taking out the green bodies from the molten Al after reaction is completed, cooling the green bodies and obtaining the in-situ three-dimensional continuously-reinforced Al-base composite material. According to the method, the in-situ three-dimensional continuously-reinforced Al-base composite material can be fast prepared through thermal explosion reaction of an Al-Ti-C system.