The invention discloses a series connection type horizontal subgrade settlement measuring device which comprises a fixing pipe, an automatic data acquisition instrument, a data converter, a transmission rod section, a guide rod section, a first limiting part, a pipe cap, a rubber buffer pad, a second limiting part, a third limiting part and a plurality of standard rod sections, wherein the transmission rod section, the guide rod section, the first limiting part, the pipe cap, the rubber buffer pad, the second limiting part, the third limiting part and the plurality of standard rod sections are arranged in the fixing pipe. The series connection type horizontal subgrade settlement measuring device disclosed by the invention can monitor the settlement amount of each interval point on the cross section of a whole filling subgrade at a time and has the characteristics of being simple in operation, low in cost and high in accuracy.