Abstract: A number of technical problems exist in the old fashioned flooting roof tanks, some of the problems are ①aged or damaged chloroprene rubber plate in pontoon sealing; ②deformed deck; ③guiding facility failure; ④corroded edge plates; ⑤derailed rolls on floating stairs; ⑥deformed tank bottom; ⑦leaking seals in the central.drains. Then some modifications are made to the tanks to solve these problems: ①add new manhole on the roof to facilitate access; ②add vapor heating system for tank cleaning; ③reduce the duration for lower part heating; ④make the bottom draining pipe act as oil discharge way as well; ⑤moldify the paraffin scraping mechanism and sealing structure; ⑥add oil barrier in the deck to reduce oil deposition; ⑦ improve the precision of the tape and add wax heater and heating devices to prevent the tape from being wax deposited.