A six-arm initiating core containing 1,3,5-triazine:N,N’,N″-tris-(4,6-dichloro——triazine-2-yl)-diethylenetriamine(3T-DETA)is synthesize from cyanuric chloride(TCT)and diethylenetriamine(DETA).The optimum reaction conditions include that n(TCT)∶n(DETA)=4∶1,N,N-diisopropylethylamine(DIPEA)is used as base,n(DIPEA)∶n(DETA)=4∶1,tetrahydrofuran as solvent,the flow rate of the THF solution of DETA and DIPEA is 0.67 mL/min,reacted at 0-5℃for 4 h and then at room temperature for 48 h,the product yield could reach to 95.3%.The structure of the target product is characterized by elementary analysis,MS,1H-NMR and FTIR.