Based on the problem of the uncertainty of fertilization position of existing liquid fertilizer deep application machine, combined with mechanical structure design and automatic control technology, a fertilizing device for deep application of liquid fertilizer with target fertilizing system was proposed, which included a liquid fertilizer deep application trencher and a liquid fertilizer target application control system. The furrow opener for deep application of liquid fertilizer was innovatively designed, the mechanical contact model between the furrow opener and soil was constructed, the dynamatic model of soil above the furrow opener was constructed, the structural parameters of the furrow opener were determined, the soil disturbed and falling principle was analyzed, and EDEM software was used to build the DEM simulation model of furrow opener-soil, the feasibility of the furrow opener structure for deep application of liquid fertilizer was verified. A target fertilizing system was developed with microcontroller as the core, using photoelectric sensor and solenoid valve synergy, the photoelectric sensor sensed the crop plant position, the speed measurement module measured the device operation speed in real time, and the microcontroller combined the crop plant position information and operation speed to control the opening and closing of the solenoid valve to complete the liquid fertilizer target fertilizing operation. The fertilizing device for deep application of liquid fertilizer with target fertilizing system was verified through field experiments. At the operation speed of 0.4~1.0m/s, the average depth of return soil was 52.8mm, the average target application rate was 84.03%, and the return performance and target application performance of the device were stable, which could meet the agronomic requirements of liquid fertilizer deep application.