The magnetic coupler for electric vehicle dynamic wireless power transfer applications has been continuously explored and optimized to meet future industrialization demands. Mutual inductance is a core parameter influencing the output characteristics of narrow track bipolar magnetic couplers. However, for the recently proposed narrow track bipolar non-salient pole magnetic coupler, an effective and convenient mutual inductance calculation model is lacking. This paper proposes an analytical method for calculating the mutual inductance of narrow track bipolar non-salient pole magnetic couplers. By providing magnetic potential boundary conditions and employing Schwarz-Christoffel transformation, an analytical relationship between mutual inductance and structural parameters is derived, and a simplified solution for mutual inductance is also presented. The established mutual inductance calculation model exhibits a calculation deviation of less than 3% at a transmission distance of 200 mm, significantly improving the calculation speed and flexibility compared to finite element simulation analysis. This provides a theoretical basis for the rapid design, parameter analysis, and optimization of narrow track bipolar non-salient pole magnetic couplers.