As a powerful supporter of mass media communication, documentary films bear a deeper social or historical responsibility than fictional images. However, historical documentaries run the risk of not being able to take on too much responsibility due to the spatial and temporal interval, for example, the comments under the documentaries on some platforms will reveal that the Hsiung-nu documentaries have not fully succeeded in guiding spectators to think about historical events with a dialectical attitude. This paper considers the causes of the biased evaluation of Hsiung-nu by the Chinese public from the perspective of documentary ontology and social factors. It concludes that ontological quality and multiple social responsibilities have stretched public trust in historical documentaries beyond their capacity; the factors like historical dilemmas, political demands, and the documentary production process make the Hsiung-nu non-objectively restored in some documentaries, leading the Chinese public away from a sufficiently dialectical view of the past. The re-examination and analysis in this paper are conducive to promoting the pursuit of realism among documentary filmmakers and cultivating dialectical thinking among spectators in documentary viewing.