NiCoFeP soft magnetic thin film used as a magnetic recording head core material was prepared by electrodeposition.Systematic studies of quaternary (NiCoFeP) thin film alloys relating their magnetic properties with film composition,grain size and the corresponding crystal structure were investigated.It was found that with increasing the concentration of malic acid in the bath,the phosphorus content in the thin film increases,the average grain size reduces,crystal structure transforms from face centered cubic (FCC) to body centered cubic (BCC),and magnetic properties of thin film decrease.Film composition altered with increasing current density,which resulted in the change of grain size and crystal structure,and magnetic properties (coercivity,remnant magnetism and squareness) of thin film were also changed.