It has been reported that heparin coexists with the hyperphosphorylated tau in the brain of the patients of Alzheimer’s disease [7] . The effect of heparin on phosphorylation by NCLK and dephosphorylation by PP2B of tau protein has been studied. Heparin was observed to improve the phosphorylation of tau, to increase the formation of tau dimers and decrease tau monomers. The first order rate constants of dimer increasing and monomer decreasing were 2 88×10 -3 s -1 and 1 74×10 -3 s -1 respectively. PP2B catalyzed dephosphorylation of the phosphorylated tau by NCLK and heparin improved such dephosphorylation. It suggests that heparin may regulate the phosphorylation and dephosphorylation of tau.