Research conclusions: We established a mathematical model between mechanical parameters(mechanical intensity, working tense , wear rate and the number of pantograph use ) and stress for studying. We can draw conclusions that the contact line mechanical reliability will decrease when train running speed, the number of pantograph and wear rate increase ; it will increase by increasing the contact line intensity , lowering the pantograph raising force and increasing the contact line working tense at a certain level. As a result, we should consider some factors such as pantograph slider to reduce wear rate when choosing the contact line. The contact line working tense should be determined by comprehensive consideration of the current-carrying between the contact line and pantograph and the reliability. When the traction power can meet the requirements , we should choose contact line with high intensity to reduce stress-strength interference area, and further increase the contact line's reliability.