Provided a complex of formula is [3-((1S, 3R)-1-biphenyl-4-ylmethyl-3-ethoxycarbonyl-1-butylcarbamoyl) propionate-(S)-3′-methyl-2′-(pentanoyl {2″-(tetrazol-5-ylate) biphenyl-4′-ylmethyl}amino) butyrate]6.XCa2+.YNa+.ZH2O, wherein X=1-3, Y=12-16, Z=9-18, and 2X+Y=18, and represented by formula (I). Also disclosed are the method of preparing the complex and the method of treating chronic heart disease using a medicament comprising the complex.