In order to address the challenges posed by limited access of large ditching-fertilizing machine in mountain orchards and insufficient power of small ditching-fertilizing machine to meet the required ditching depth, as well as the limited functionality of most small ditching-fertilizing machine, a compact vertical spiral ditching-fertilizing machine was developed for efficient integration of ditching, fertilization, and soil covering functions in hilly orchards with 25° slope. Through theoretical analysis, the key components such as ditching device, fertilizing device and soil covering device were designed. The Hertz-Mindlin with Bonding contact model was selected to establish the ditching simulation model, taking into account the soil compaction characteristics in hilly orchards. Using the ditching rotation power consumption, forward power consumption and specific power consumption as indexes, the Box-Behnken simulation test was conducted to optimize the structure parameters of spiral ditching opener. The optimization results were as follows: the optimal spiral angle, number of teeth, edge angle and tooth length of the opener were 17.6°, 10, 30° and 19.76 mm, respectively, and the rotational power consumption, forward power consumption and specific power of the opener with optimal parameters were 6.74 kW, 0.132 kW and 0.165 kW·h/kg, respectively. The opener with optimal parameters was fabricated and the experiment was conducted to validate the simulation. The results showed that the relative error of the ditching rotation power between experiment and simulation was 5.6%, indicating that the opener optimization results were correct. Field test results of the machine showed that the stability coefficient of ditching depth, consistency coefficient of ditching bottom width, uniformity coefficient of fertilization and soil coving rate were 96.91%，98.16%，97.08% and 77.38%, respectively, and all indexes of the ditching-fertilizing machine met the agronomic requirements.