Disclosed is a composite pellet used as a raw material in a kiln process for the production of phosphoric acid, which is of a core-shell structure with an inner ball encapsulated with a shell, the inner ball mainly consists of a inner ball material and a binding agent, and the shell mainly consists of a cladding material and a binding agent; the inner ball material mainly consists of a carbonaceous reductant powder, and phosphate ore powder and silica powder, the inner ball is combined with the shell through the binding agent to form the core-shell shaped structure. The preparation of the composite pellets comprises the steps of preparing the inner ball, preparing the cladding material, forming, drying and solidifying composite green pellets etc. The composite pellets prepared by the present invention have a smaller range of formulation fluctuation, more stable quality, higher strength and better performance.