Weidong currently serves as the Director General of the Policy and Planning Department of the Foreign Ministry.
The current envoy to India Luo Zhaouhi has been appointed as Vice Minister of Foreign Affairs. He will be succeeded by Sun.
An agreement has been conveyed by India to China on Sun's appointment, Indian Embassy officials here told news agency PTI.
Indian Ambassador to China, Vikram Misri, congratulated Sun on his appointment through a tweet.
"Congratulations to His Excellency Sun Weidong, who has been appointed as the new Ambassador of the People's Republic of China to India - had the opportunity to welcome him home recently in Beijing and wish him all the best for his important mission," Misri said.
Sun, who specialises in China and South Asia relations, interacted closely with Jaishankar during his tenure in Beijing as the Indian ambassador from 2009 to 2013.
Sun was the Deputy Director General during the tenure of Jaishankar.
Misri also called on Luo who took over as the Vice Foreign Minister (WFM) of China.
"Ambassador @VikramMisri met Vice Foreign Minister and former Ambassador to India Luo Zhaohui. Ambassador congratulated Mr Luo for assuming charge as VFM. The two sides used the opportunity to compare notes on the upcoming engagements in bilateral relations," the Indian Embassy here said in a tweet earlier.
A Chinese official said that an official announcement about new Ambassador's appointment would be made after due administrative process.
Sun is well-versed with issues related to India-China relations.