Potato (Solanum tuberosum L.), the fourth-largest staple crop in China, is widely cultivated in the northwest dryland farming regions. Focusing on the typical operating conditions in northwest terraced fields, where plots are small, irregularly shaped, and roads are narrow, which caused significant difficulties for potato combine harvesters when turning and maneuvering in the field. The predominant planting method in this region involved large ridged double-row planting with black plastic film covering and soil placed on top. Many harvesters in the area faced issues such as low operational efficiency, poor tuber-soil separation performance, high tuber damage rates, and high impurity rates. To address these challenges, a potato combine harvester based on multiple steering modes and anti adhesion soil fragmentation type was designed. This harvester can simultaneously perform multiple operations, including digging, tuber-soil separation, membrane separation, surface soil cleaning, sorting, collection, bagging, and automatic unloading. The overall structure of the machine and its key operational parameters were determined based on the harvesting agronomic requirements and field conditions in the primary potato-producing areas of northwest terraced fields. Initially, relevant design principles from automotive and tractor engineering were applied to determine the structure and key parameters of a multi-mode steering wheeled chassis. Furthermore, inspired by the burrowing principle of the northwest mole’s head, bionic research methods were employed. Using 3D scanning technology and reverse engineering, the geometric parameters of the mole’s head were obtained, and a composite biomimetic wedge-shaped digging shovel device was designed. A dynamics model analysis approach was then used to specifically determine the operational parameters and force analysis for the multi-mode steering wheeled chassis, the composite biomimetic wedge-shaped digging shovel device, the soil-crumbling separation and conveying device, agricultural film and seedling removal device, as well as the manual impurity removal and automatic grading device. Based on these research findings, the entire machine was thoroughly designed by using 3D modeling and 2D drafting, and a prototype was manufactured. Field tests were conducted, and the results showed that the loss rate was 1.98%, the tuber damage rate was 1.59%, the skin-breaking rate was 2.15%, the impurity rate was 1.84%, and the productivity ranged from 0.21hm2/h to 0.36hm2/h. The potato combine harvester based on multiple steering modes and anti-adhesion soil fragmentation type met national and industry standards in all test indicators, providing valuable reference for the mechanization of potato harvesting in northwest dryland areas.