The structure improvement design of the traditional fixed pedrail robot is carried out to make the guide wheel angle can be adjusted and the pedrail can be automatic tensioned after adjustment. The theoretical calculation analysis of the obstacle- navigation ability of the pedrail robot is carried out,the change trend of the center of mass is detected by using pro / E modeling,and the optimization of center of mass is carried out. The optimization result show that,through adjusting the angle of front guide wheel,the obstacle- navigation height,span,groove width and climbing angle of fixed robot are improved,the feasibility of the improved robot is verified. Compared with the traditional fixed tracked robot,the obstacle- navigation ability can improve and enhance,compared with four swing arms tracked robot,it has the advantages of traditional fixed tracked robot.