Reuters has not been able to reach Sun or a representative for comment since he was put under investigation a year ago. He expressed regret and remorse for taking millions of dollars in bribes.
Sun said he would not appeal the sentence.
His wealth was confiscated and his political rights were stripped for the rest of his life, according to the verdict.
After Sun was detained last July, the path was clear for Xi to promote loyal ally Chen Min'er in Chongqing.
A former top Chinese Communist Party official, who was accused of plotting a coup against President Xi Jinping previous year, was today sentenced to life imprisonment for taking Dollars 26.7 million in bribes. Sun was sent to Chongqing to fill the void left by Bo, but he failed to wipe out his predecessor's "lingering pernicious influence", Communist Party of China investigators determined.More news: Justify justifies hype with Kentucky Derby win
Many China politics experts and some party insiders attribute Mr. Sun's downfall to his reputation as a possible next-generation leader whose ties were to senior party figures other than Mr. Xi.
Since Mr Xi came to power in 2012 he has made tracking down corrupt elite "tigers" and "flies" at the grassroots level a cornerstone of his administration and hundreds of thousands of officials have been punished as part of the campaign.
He was abruptly removed from office ahead of the party Congress in October a year ago.
China's parliament also removed the two-term limit for the president paving the way for Xi to continue in power for life.
The Chinese president said in April, though, that he is opposed to life-long rule, arguing that the move to amend the constitution was definitely misinterpreted by foreign observers.
Sun was the youngest member of the Communist Party's top 25-member Politburo before he was expelled and he was widely considered a potential successor to Xi.