The　tie　rod　is　one　of　the　key　components　affecting　the　steering　stability　and　reliability　in　the　steering　system　of　heavy　vehicles.　In　order　to　meet　the　heavy　load　steering　requirements　of　heavy　vehicles,　the　steering　system　is　universally　the　electro-hydraulic　power　steering　system　(EHPSS).　The　hydraulic　actuators　used　in　the　EHPSS　are　double　hydraulic　cylinders,　which　are　connected　in　series　and　symmetrically　installed　in　this　study.　The　hydraulic　drive　system　in　the　steering　system　will　affect　the　steering　mechanism　of　stress　state,　leading　to　the　tension　of　the　tie　rod　in　most　working　conditions.　The　tie　rod　be　compressed　only　in　extremely　unequal　loading　of　dual-tires.　The　tie　rod　force　model　is　established　based　on　Lagrange　equation　and　verified　by　the　tie　rod　test　platform.　Three　key　parameters　describing　the　force　rule　of　tie　rod　are　obtained　by　adopting　quasi-steady　state　analysis　method,　including　pump　pressure,　difference　value　and　sum　value　of　left　and　right　tires　steering　resistance　torque.　Pump　pressure　is　the　key　factor　affecting　the　tie　rod　force.　The　higher　the　pump　pressure　is,　the　greater　the　pull　force　of　tie　rod　is.　The　steering　resistance　torque　will　further　affect　the　variation　law　of　the　tie　rod　force.　In　the　analysis　when　the　tire　at　middle　position,　with　the　increase　of　difference　value　of　steering　resistance　torque,　the　tie　rod　force　offset　between　loading　conditions　and　no-load　conditions　increases.　When　the　tire　turns　from　the　middle　to　both　sides,　the　increase　of　sum　value　of　steering　resistance　torque　will　result　in　the　rising　of　tie　rod　force　change　rate.　This　study　reveals　the　variation　law　and　key　parameters　of　the　tie　rod　force　of　heavy　vehicles.　It　can　provide　basis　for　stability　and　reliability　design　of　steering　system.　©　IMechE　2020.