Abstract: To meet the needs for frequent measurement of humidity and other nutrient contents in soils for growing watermelon, and to solve the problems of high labor intensity and bad working environment during manual data collection in the watermelon greenhouse that are caused by high density of potted plants and narrow space among the potted plants, we designed an electrically self-propelled soil data collection device. The mobile platform of this device can move to a desired position near a potted plant along a preset track, a multi-joint manipulator on the device inserts into the soil of the potted plant and collects humidity information from the soil automatically. In this paper, the structures of the device, the multi-joint manipulator and the detection component on the device were designed. Moreover, the control system and communication system of the device were also established. Based on this device, experiments were carried out to detect soil humidity. The experimental results showed that the maximum speed of the device was 0.24 m/s in the pre-planned path; the multi-joint manipulator with sensor could accurately insert into the soil with the maximum horizontal positioning error of 11 mm, a loss rate of potting detection of 0.92% and the efficiency of soil data collection of 3.2 pots/min. The device can realize automatic collection of soil data in all potted plants via cyclic turning inspection instead of manual work. The research indicated that the designed device increased the efficiency of data collection in comparison with manual collection, and it could meet the requirements for high frequency and high throughput information collection of potted soil.