In the men's first round, third-seeded Mikhail Youzhny, also of Russia, defeated Horacio Zeballos of Argentina 6-1, 7-6 (5).
The 17th-ranked Petrova had little trouble against Buchina, runner-up at the junior US Open, who was playing in her first WTA Tour event courtesy of a wild card. Petrova, runner-up in 2006, broke Buchina twice in the first set and closed out the match in just 48 minutes.
"The match was so short and she (Buchina) was so nervous that it wasn't going her way," said Petrova.
In the next round Petrova will face Alona Bondarenko of Ukraine, who beat the 2006 champion Anna Chakvetadze 6-4, 6-3.
Later, Maria Jose Martinez Sanchez of Spain beat seventh-seeded Dominika Cibulkova of Slovakia, 6-2, 6-2.
Youzhny, who is looking for his first title this season, won six consecutive games to take the first set but had a harder time in the second.
"He (Zeballos) made too many mistakes in the first set," Youzhny said. "But in the second set, I was not that concentrated while he was serving and returning much better."
Zeballos saved two match points on a second-set tiebreaker before Youzhny closed out the match with a forehand winner.
The 20th edition of the dual ATP and WTA Kremlin Cup has a weakened women's draw because seven of the world's top players have already qualified for next week's season-ending WTA Championships in Doha and so have opted to skip the Moscow tournament.
Defending champion Jelena Jankovic, runner-up Vera Zvonareva and Agnieszka Radwanska lead the women's draw and will compete for the remaining spot in Doha.
World No.7 Nikolay Davydenko, fresh from winning the Shanghai Masters on Sunday, tops the men's draw. He is scheduled to face Marat Safin in the first round on Wednesday.