Abstract: This paper reviews geochronological and geochemical data on Mesozoic -Cenozoic magmatism in North China.It is suggested that the temporal variation in geochemistry of Mesozoic-Cenozoic mafic rocks is coupled with lithospheric thinning process in this region. Consequently,the duration of magmatism(180～90 Ma)provides a first-order estimation for the timescale of lithospheric thinning in this region.The relatively long timescale(～100 Ma)suggests that thermomechanical erosion by convective mantle is the main mechanism of lithospheric thinning. Contrasting magmatic evolution trends in western and eastern North China craton suggest that lithospheric thining may have proceeded in diachronous manner.