The invention provides a single phase grounding fault line selection method for medium voltage distribution networks based on fault process analysis, which comprises the steps of calculating neutral point voltage, determining whether the neutral point voltage exceeds a preset threshold value, diagnosing fault type, determining whether the fault is a single phase grounding fault, describing fault process, positioning line selection area, selecting line for the fault, outputting result and finishing. The method can reflect the process of fault development and evolution intuitively and constitutionally, effectively selects the line for stable grounding with single phase grounding fault time more than 500 milliseconds, and can totally capture and describe transient fault during the fault process.