Magnetic Guidance Technology can meet the precise measurement requirements when drilling steam-assisted gravity drainage (SAGD) oil wells. Magnetic generator is a key part in the Magnetic Guidance Technology. When magnetic generator is tripped into horizontal well, pump pressure and passing capacity of the magnetic source generator in the curved section need to be analyzed. So, a mathematical model of tripping in the magnetic generator is established. If curvature radius, deviation angle, and friction factor are known, the forces acting on the magnetic generator in different positions could be calculated. The finite element (FE) results show that: (1) with depth increasing in the curved section, the equivalent stress on the magnetic generator increases in a fluctuating manner, the contact area, friction drag, and energy loss increase. (2) The greater the hole curvature, the greater tripping in force and the higher pump pressure are needed. The lower friction coefficient is favorable to tripping in the magnetic generator. (3) The friction between the magnetic generator and tubing wall in the horizontal section is much less than that in the curved section. Field applications have shown that the maximum downforce is close to the result of finite element analysis. The research results provide a reasonable reference basis for smooth running of magnetic source generators with different trajectory conditions.