Research conclusions:(1)The factors of untwining scheme mainly include:number and location of the introduction line，number of positive lines and carrying capacity，trend and characteristics of passenger and cargo flow, features and configurations of station. ( 2 ) The traditional untwining scheme can be divided into three types which are mainly passing flow, crossing flow and mixing flow. The dividing pathways are flexible，but the untwining is difficult with restricted length of station and topography.(3)The main features of half access type untwining scheme is joining with one of the station throat，it can be divided into four fundamental types in I,II,III,IV quadrant，and the others can be expanded based on the fundamental type.(4)The half access type untwining scheme has the characteristic of fighting favorable conditions for raising or lowering the elevation，lower project costs，lower construction difficulty contrast to the traditional untwining scheme. It can be especially applicable with limited slope，significant traffic and part of the flow having fixed path.