There is a newly-opened seamount Japanese cuisine in Xibahe Yuanfang Hotel. There is a Japanese cuisine buffet in 68 yuan and 98 yuan (68 yuan's is recommended), or you can take a bus to Xibahe north at the northeast third ring road, and there is an intersection of Crab Lao Song in the inner ring road 100 meters away.
There is also a seafood buffet in Liangmaqiao Building, but the price is more expensive 160 yuan, but you can eat abalone and lobster, hehe.
I heard that the 98 yuan self-help in the VIP building of Beijing Hotel is also good, but I have never been there. You can try it, and the grade is not a problem.