Research conclusions:(1)The fundamental conditions of CTCS-3 to CTCS-2 level transition is:the distance from YG-3/2 balise group to the CZ balise group should be greater than 450 m，the distance from the YG-3/2 balise group to ZX-3/2 balise group should be greater than Ss traveled distance at maximum allowable line speed，the scope of the RBC data configuration should extend at least one braking distance from the execution point.(2)When two CTCS-3 yards in a row integrate and belong to two different RBC，the CTCS-3 to CTCS-2 level transition can be carried out on the cross-field line between the two yard，the CTCS-3 to CTCS-2 level transition can be carried out after running across the cross-field lines，then it achieves the RBC handover.(3)When two CTCS-3 and CTCS-2 yards in a row integrate and have more than two cross-field lines，CTCS-3 to CTCS-2 level transition can be carried on two cross- field lines. (4)When the length of the cross-field line between CTCS-3 yard to CTCS-2 yard does not meet the basic conditions of level transition，the CTCS-3 to CTCS-2 level transition point can be set on the CTCS-2 line. (5)The research conclusions can provide a reference for the signal design of train control system when there exists cross -filed line.