The electromagnetic valve driving mechanism is the significant equipment, which plays a vital role in the unit pump injection system; therefore, the performance of the electromagnetic valve directly influences the function of the control system. Based on the operation conditions of the unit pump injection system, a steady electromagnetic valve model was modified to study the influence factors of electromagnetic force and the best combination to get the maximum electromagnetic force. The validation model was verified by experiment. The effects of some crucial parameters upon the electromagnetic force were investigated in the present paper, (including working airspace, magnetic pole’s cross-sectional area, coil position, coil turn, the armature thickness). The results show that the electromagnetic force of the solenoid valve enhanced with the increase of driving current and with the decrease of working airspace. Besides that, the electromagnetic force won’t continuously rise if the driving current goes up to the threshold. Such results seem can be employed to explain the magnetic saturation phenomenon. In addition, the electromagnetic force will correspondingly rise with the increasing of armature thickness, increasing of coil turns, closing the coil’s position towards armature’s centre and equalizing the cross-sectional areas of major and vice poles. Based on the calculation, the greatest electromagnetic force was obtained by means of orthogonal design. The results prove that the method is feasible and accurate to obtain the key parameters of the solenoid valve in order to achieve the greatest electromagnetic force. The research results have a great engineering significance to the promotion of the electromagnetic force.