Abstract: The present disclosure provides an active metal-containing M-CHA/M-MOR composite molecular sieve and a preparation method. The preparation method includes: S1, adding an alkali source, a silicon source, an aluminum source, a structure-directing agent, an active metal complex and a crystal form modifier into water, and performing stirring to obtain a gel, wherein the crystal form modifier is an aqueous solution containing a molecular sieve secondary structural unit prepared based on at least one of an MOR molecular sieve, a CHA/MOR composite molecular sieve, and a CHA-MOR mixed molecular sieve; S2, subjecting the gel to a hydrothermal reaction, and separating the resulting slurry to obtain a composite molecular sieve; and S3, drying the composite molecular sieve, and performing calcining to obtain the active metal-containing M-CHA/M-MOR composite molecular sieve. The direct preparation method has the advantages of short process flow, low wastewater production, low energy consumption and the like.