Honduran Emil Martinez grabbed a hat-trick and defender Zhou Ting added a penalty in front of a 60,000 crowd at the Workers' Stadium to win the capital club their first championship since a professional national league was formed in 1994.
"I'm really ecstatic. This day has taken Guoan more than a decade to achieve," China midfielder Tao Wei, who has spent 11 years at the club, told state media.
The striker doubled Beijing's lead five minutes into the second half with a fierce left-footed drive from the wing and, after Zhou had made it three from the spot, claimed his hat-trick with a similar strike from closer range.
Beijing, owned by China's largest financial conglomerate and one of the best-funded clubs in the CSL, sacked South Korean coach Lee Jang-soo last month after suffering their first home defeat of the year.
"We've been through many difficulties to get to this point," said team manager Zhang Lu. "I was quite worried but it all turned out okay."
