In the system of phraseology, comparative phraseological units with the word how in Russian and the word như in Vietnamese occupy a significant place. Russian and Vietnamese comparative phraseological units with the names of natural phenomena are the key to understanding the people’s culture, their history, ideas about the world around them. Based on the analysis of the material collected from various explanatory and phraseological dictionaries of the Russian and Vietnamese languages, from the card index of the academic dictionary of the Vietnamese language, from fiction, in this article we intend to pay greater attention to highlighting the problem of comparing Russian comparative phraseological units with the word «how» and Vietnamese equivalents with the word «như», denoting natural and natural phenomena.