Research conclusions：Through the research on track gauge widening rules of small turnout and comprehensive consideration of the curve geometry, type of blade, gauge at entry of turnout, gauge at toe of blade, gauge in diverging track, etc, the analyses of the reason for structure widening in switch panel are made, the calculation methods for structure widening in any case are put forward, the definition on structure widening is given and a general calculation program for turnout structure widening is developed.