A hydroxylapatite (HA) coating was produced by means of bionic mineralizing in a fast calcific solution(FCS)at room temperature. The pH changes of FCS during the deposition process were measured. The supersaturations of various calcium phosphates formed during FCS were compared, during which that of HA was found to be the greatest. Optimnal thermodynamic conditions were important for the formation of HA coatings in the bionic mineralizing process.