In order to explore the effect of cladding β-cyclodextrin（β-CD）on the viscosity and viscosity-average molecular weight of amphiphilic polymers，such as acrylamide，acrylic acid，cetyl allylammonium chloride terpolymer（APC₁₆），the viscosity variation law and influencing factors of β-CD cladding APC₁₆ solution were studied by rheometer. The characteristic viscosity of APC₁₆ inclusion system was determined by Urkovinometer，and then the viscosity-average molecular weight of APC₁₆ without intermolecular interaction was accurately calculated. The results showed that under the condition of 45 ℃ and 30 g/L salinity，the critical association concentration of APC₁₆ solution shifted to 5300 mg/L when the molar ratio of β-CD and APC₁₆ was 1∶2. When the molar ratio of β-CD and APC₁₆ was 1∶1（complete inclusion ratio），the critical association behavior of APC₁₆ solution disappeared. Under the complete inclusion ratio，the viscous flow activation energy of the cladding system was smaller than that of APC₁₆ solution when the temperature increased from 25 ℃ to 90 ℃. The viscosity of the cladding system decreased more gently with the increase of NaCl concentration，while the cladding strength increased. Accordingly，the viscosity-average molecular weight of amphiphilic polymers could be determined by the β-CD inclusion method based on host-guest interaction. The viscosity-average molecular weight of APC₁₆ was 537×10⁴ Da，while that of HPAM was 1292×10⁴ Da. When the molar ratio of β-CD and APC₁₆ was 1∶1 and 2∶1，the viscosity-average molecular weight of APC₁₆ was 341×10⁴ Da and 358×10⁴ Da，respectively. When the molar ratio of β-CD and HPAM was 1∶1 and 2∶1，the viscosity-average molecular weight of HPAM was 1223×10⁴Da and 1272× 10⁴ Da，respectively. The viscosity-average molecular weight of HPAM was consistent before and after inclusion. The effectiveness of the legal determination of molecular weight of amphiphilic polymers by the β-CD inclusion method was confirmed. A new method was provided for the contribution of hydrophobic action of amphiphilic polymers to viscosity and molecular weight determination.