Abstract: A large number of crossing engineering undercross existing roads of newly-built railway lines appear with rapid development of railway construction.Too large settlement due to tunnel construction can affect riding safety and comfort on highway.Therefor,uniform subsidence control standard for undercrossing tunnel construction should be studied and established urgently.Based on comparison of demand on safety and comfort in road operation,the surface evenness for comfort demand is supposed to control the differential settlement of road surface;the orthogonal test technique is adopted for numerical simulation of road surface settlement to reveal the relationship between the highway evenness demand and the maximum road surface settlement;the allowable value and rate of road surface settlement due to construction below are proposed for highway of different classification and with different pavement structure.