The invention provides a monitoring process for an underground three-dimensional transportation process of LNAPLs (Light Non-Aqueous Phase Liquids). The monitoring system comprises a resistivity detection device and a high-density resistivity monitoring device, wherein the resistivity detection device comprises a resistivity detection rod, a data acquisition module, an upper computer and a remote transmission module; the resistivity detection rod is connected with the data acquisition module and the remote transmission module through lead wires; the remote transmission module is connected with the remote upper computer through a GPRS (General Packet Radio Service) antenna; the high-density resistivity monitoring device is arranged on one side of the resistivity detection device; the high-density resistivity monitoring device comprises a plurality of uniformly distributed electrodes; the electrodes are connected into a resistivity meter through lead wires; the resistivity meter is connected into a computer. The monitoring process for the underground three-dimensional transportation process of the LNAPLs is simple in structure and convenient to operate; by the resistivity detection device, automatic monitoring can be realized, and the monitoring efficiency is improved; furthermore, monitored data can be transmitted in real time, and automatic alarming can be realized.