The present invention discloses a non-supported catalyst comprising: an active metal oxide and an additive embedded in the outer surface of the active metal oxide; the active metal oxide is selected from one oxide or more oxides of iron, cobalt, nickel and copper; the additive is selected from one or more elements of iron, cobalt, nickel, copper, rhodium, manganese, potassium, silver, calcium, magnesium, zirconium, aluminum, zinc, ruthenium, platinum, sodium and phosphorus, and is in the form of an element or an oxide; the catalyst achieves the effective coordination of the supported additive and the active metal oxide, the additive can act directly on the surface of active ingredients, the promoting effect of the additive can be significantly enhanced, reducing of the active ingredients can be effectively promoted, reactivity is improved, and the catalytic properties of the catalyst can be improved. The present invention also discloses a preparation method of the non-supported catalyst.