The invention discloses a multi-material powder supplying and laying device for powder bed melting and a control method of the multi-material powder supplying and laying device. A plurality of powderinlets are formed in the upper end of a main powder storage tank, an independent sub-powder storage tank is installed at each powder inlet, and powder in the sub-powder storage tanks are premixed by the main powder storage tank, then a powder mixer in a powder mixing device is used for mixing the premixed mixture, the main powder storage tank and the powder mixing device are adopted for premixingand sufficient mixing respectively, the powder mixing device serves as a buffer section, the powder mixing printing efficiency is improved, and meanwhile printing materials of different mixing contents and types can be added through the plurality of sub-powder storage tanks; and a printing moving frame is used for driving a powder spray head to spray powder, manufacturing of a functionally gradedmaterial and a multi-component alloy / high-entropy alloy-based composite material with components continuously changing in any direction is achieved, long powder mixing time is saved, real-time powderlaying and real-time machining can be achieved, the production cycle is greatly shortened, the production cost is greatly reduced, and the production efficiency is improved.