The invention relates to a metal-chromium-complex-packaged composite FAU type molecular sieve and a synthetic method thereof. A soluble chromium salt, 3-aminopropyltriethoxysilane, an aluminum source and a silicon source are adopted as raw materials and the composite FAU type molecular sieve is synthesized by one step through a hydrothermal method. The synthetic method includes steps of adding the soluble chromium salt, the 3-aminopropyltriethoxysilane, the aluminum source, sodium hydroxide and the silicon source in order into a reactor, reacting under stirring, adding initial gel into an autoclave, crystallizing, naturally cooling the reaction product to room temperature, washing the product with water until neutrality, and calcinating the product at 350-400 DEG C for 3-6 h to obtain a final product. The metal Cr is packaged in the FAU type molecular sieve through a zeolite synthesis process. According to the composite FAU type molecular sieve and the synthetic method, product dispersibility is good, large-particle aggregation does not occur, surfaces are clean, industrial application is easy, preparation steps are simple and industrial production is convenient.