The work aims to study the factors influencing the cap removal torque of oral solution and regard them as the theoretical basis for developing the specifications for filling, capping and test of oral solution. The above-mentioned influence factors included the capping torque, the contact between inner cap seal and solution and the duration after capping. Single-factor experiment and independent sample t-test were applied to study these influence factors. The results were as follows: Cap removal torque was increased with capping torque when capping torque was in the range of 136-226 N•cm. After the inner cap seal was in contact with solution for 1 h, the cap removal torque was increased significantly. After the cap was tightened with 169 N•cm, the cap removal torque was increased with the extended duration. In conclusion, the cap removal torque of oral solution is affected by many factors, including the capping torque, the contact between inner cap seal and solution and the duration after capping. To keep the cap removal torque in an appropriate range, these factors should be controlled during the packaging, inspection, transportation and storage of oral solution. In addition, the trend of cap removal torque varying with capping torque and duration can provide data support for the parameter setting of production process.