The invention aims to provide porous nano-sized biological multicalcium and application thereof. The provided biological multicalcium is absorbed by a human body more easily, is convenient to use, and is safer; the porous nano-sized biological multicalcium is prepared by using a yak bone, hyacinth beans, a turtle shell, a cuttle bone, tortoise plastron and pearl mother as raw materials, and is prepared through performing freeze drying, superfine grinding, enzymolysis, electromagnetic wave treatment and the like to the raw materials. Through application of characteristics of the porous nano-sized biological multicalcium, vitamin D3 is contained into pores of the porous nano-sized biological multicalcium so as to prepare biological calcium D3 tablets, chewable tablets, capsules, granules, suspensions, and calcium-supplementing preparations.