Bolshunov covered the distance in 1 hour 8 minutes 52.9 seconds.
The second place was taken by Ivan Yakimushkin, 47.1 seconds behind Bolshunov.
Andrey Larkov is in third place.
The Russian cross-country skiing championship runs from March 27 to April 4.
Earlier it was reported that Sorina won the skiathlon at the Russian cross-country skiing championship.