Ammonia is an important chemical for producing fertilizer and also an important carbon-free energy carrier. Haber-Bosch process is the main method to synthesize ammonia. However, it suffers from some severe problems, such as the high energy consumption, the massive emission of greenhouse gas CO₂ and the poor catalytic efficiency. Recently, ammonia synthesis based on electrocatalytic nitrogen reduction reaction (NRR) by using renewable energy under mild reaction conditions has attracted wide research attention. In addition, the raw materials (N₂ + H₂O) are earth abundant. Although great advances have been achieved in electrocatalytic NRR field, some challenges including the high-cost of noble metal based electrocatalysts, the low ammonia yield and unsatisfactory Faradaic efficiency, as well as the unexplored catalytic mechanism of NRR still exist. In this review, we summarize the recent advances in electrocatalytic NRR field based on heterogeneous catalysts. Firstly, we discuss the catalytic thermodynamics and reaction mechanisms towards NRR. Secondly, a range of recently reported non-noble metal included catalysts are surveyed, including transition metal oxides/nitrides/sulfides, metal-free materials and single-metal-atom catalysts. Then, some promising strategies to enhance the catalytic activity, selectivity and efficiency are proposed, and the main methods for the determination of ammonia are also mentioned. Finally, the challenges remaining to be solved are summarized, and future perspectives are also presented.