The invention is applicable to the field of metal powder alloy and provides an inorganic binder used for a metal soft magnetic powder core, the metal soft magnetic powder core and a preparation method of the metal soft magnetic powder core. The inorganic binder comprises the following formula components of, by the total weight of 100%, a matrix, a curing agent, a skeletal material and an additive, wherein the matrix is an aluminum phosphate matrix. The inorganic binder serves as the binder of the metal soft magnetic powder core. According to the inorganic binder provided by the invention, the binding effect is good, and meanwhile the requirements for the total inorganic performance, indecomposition of heat treatment, low-temperature curing, the ageing resistance and meeting of the ROSH standard are met.