The invention provides a preparation method of 6XXX-series in-situ aluminum-based composite material powder for laser additive manufacturing. The preparation method of the 6XXX-series in-situ aluminum-based composite material powder for laser additive manufacturing comprises the steps of heating commercially pure aluminum, covering through a high-temperature covering agent, and heating for smelting; uniformly mixing KBF4 and K2TiF6, drying, and adding into a melt; after reaction, sequentially adding a required intermediate alloy and commercially pure Mg, adding a refining agent into the melt for degassing and refining, and then carrying out gas atomization; and obtaining the 6XXX-series in-situ aluminum-based composite material powder for laser additive manufacturing. According to the method, the in-situ TiB2 micro-nano-particle reinforced 6XXX-series composite material is prepared by adopting an in-situ melt growth and high-temperature gas atomization method, and through preparing theTiB2 particle reinforced aluminum-based composite material powder, TiB2 particles are uniformly and dispersedly distributed in an aluminum matrix. The aluminum-based composite material powder prepared through the method has favorable laser absorptivity and is applicable to a laser additive manufacturing technology.