As a promising conversion technology, electrochemical nitrate reduction reaction can continuously extract ammonia from harmful wastewater efficiently and environmentally. The improvement of ammonia production efficiency by inhibiting side reactions is inseparable from the continuous development of advanced catalysts. The advantages of high atomic utilization, large specific surface area, and high selectivity have led to the full attention of single-atom catalysts, which enables atomically dispersed catalysts to be used in electrochemical nitrate reduction reactions (NO₃RR). Meanwhile, as a single-atom loading platform, the support is crucial to the improvement of catalytic activity, efficiency and working stability. Reasonable support design and construction play a guiding role in the preparation of advanced catalysts. In this review, it is focused on support design of single-atom catalysts for NO₃RR, aiming to highlight the correlation between single atom support and catalytic mechanism. Then the latest research progress of different supports of advanced catalysts is provided, and the design of different supports are further summarized. This review provides valuable ideas and practical guidance for the rational design of single-atom catalysts for electrochemical NO₃RR, which is expected to promote them to solve existing problems, guide them from exploration under laboratory conditions to industrial production, and eventually provide potential answers for actual production.