Calculations of synthetic spectra with the Zeeman magnetic splitting of lithium and rare earth (Ce II, Nd II, Sm II and others) lines for the roAp-star HD 101065 (Przybylski's star) in a spectral region of 670.58 to 670.87 nm were carried out to fit to an observed spectrum near the lithium line λ = 670.8 nm. The hyperfine structure of lithium lines are taken into account in detailed calculations. This allowed us to evaluate the influence of magnetic splitting on estimates of the lithium abundance in the star atmosphere and a value of the isotopic ratio ⁶Li/⁷Li.