Magnetic fluid seal(MFS) is one of the most mature applications of magnetic fluid(MF) and is widely used in numerous fields. When applying the MFS at − 55 ℃(the low temperature), it will lead to a high initial torque situation and a noticeable seal capacity reduction. This situation results in sealing failure and impedes the normal device startup. In this study, we synthesized MF based on polyalpha-olefins-3.5 (PAO-3.5), demonstrating fluidity at − 55 ℃, a saturated magnetization of 46.7 kA/m, and stability exceeding 2 months. The low pour point of PAO-3.5 based MF positions them as a good material choice for MFS applications in low temperature. And a structure of field-controlled MFS to control the magnetic field in sealing gap was proposed. To emphasis the necessity of the control of magnetic field, empirical equations were employed to model the viscosity and yield stress of MF under varying magnetic field strengths and temperatures, explaining the impacts of these factors. And the starting torque of MFS in specific conditions can be predicted. Notably, the use of field-controlled MFS have decreases in starting torque during non-pressure-resistant scenario, pressure-resistant scenario and long-term use.