Low-molecular-weight polyisobutylene ( LMPIB) has a superb prospect in the preparation of viscosity reference materials due to its superb thermal stability, chymic rebellion and weather fastness. Because of the yauld α-olefin and β-olefin of LMPIB commercially available, LMPIB is prone to oxidation and crosslinking reactions, which results in great changes in viscosity. The change of viscosity is contrary to the principle of uniformity and stability of viscosity standard substances, which limits its application in the field of standard substances. The stable modified LMPIB polymer was obtained by thiol-ene click reaction and used in the synthesis of viscosity standard substances. Firstly, the obtained modified LMPIB was tested by ¹H-NMR and FT-IR and calculated the content of olefin in the low-activity LMPIB. Finally, a stable Newtonian modified LMPIB fluid was obtained after the test of its fluid Newtonian property by rheometer and the change of viscosity over time. In other words, the modified LMPIB may be used in the application of viscosity reference material, which provides a new idea for the next preparation of viscosity reference material.