The invention discloses a preparation method of a water soluble phenolic resin crosslinking agent for temporary plugging steering acidizing, relates to an oilfield chemical agent, and in particular, relates to a preparation method for an acidizing additive. The preparation method comprises the steps: heating phenol to melt, then adding an NaOH aqueous solution, heating to 60 DEG C, then adding formaldehyde, and carrying out a first alkali catalytic reaction under a stirring condition; and then adding an NaOH aqueous solution again, heating up to 85 DEG C, adding formaldehyde, carrying out a second alkali catalytic reaction, and thus obtaining the water soluble phenolic resin after the second alkali catalytic reaction is finished. The water soluble phenolic resin crosslinking agent prepared by the method is suitable for a chemical crosslinking temporary plugging agent depended by chemical steering in the oilfield steering acidizing technology; the chemical crosslinking temporary plugging agent prepared by the method has the advantages of bright color and good water solubility. The chemical crosslinking temporary plugging agent has the technical advantages of strong temporary plugging steering capability, good steering effect, and difficult causing of secondary damage to a reservoir stratum, and can be widely used in oilfield oil water well acidizing measures.