Abstract: A hyperbranched amino modified polysiloxane was synthesized via ring-opening reaction of epoxy, by polydimethylsiloxane double-terminated with epoxy and diethylenetriamine as raw materials, and the modified polysiloxane emulsion was prepared. The effect of synthesis factors on the conversion rate of epoxy were researched, the condition of synthesis was optimized, the effect of molecular weight of polysiloxane on the properties of the emulsion of modified polysiloxane and its finished fabric were studied, and the properties of the emulsion of modified polysiloxane and its finished fabric were measured. The results showed that: as the relative molecular weight of polysiloxane was about 3100, the amount of substance ratio of polydimethylsiloxane double-terminated with epoxy to diethylenetriamine was 1.5:1, the temperature of reaction was 80 ℃, the time of reaction was 3 h, and the dosages of isopropyl alcohol as dissolvent was 30%wt, the epoxy conversion rate was 93.25%, the emulsion of synthetic products had excellent stable property and no floating oil, the average particle size of the emulsion was 56 nm. Compared with amino silicone and block polyether modified amino silicone, the fabric finished by the modified polysiloxane had lower yellowing, better softness and hydrophilic.