B-type flexible cast iron pipes and fittings are produced based on GB/T12772-2008 “flexible interface cast iron drainage pipes, fittings and accessories” standard, which integrates the merits of both W-type and A-type cast iron pipes. The straight pipe section uses W-type socket-free casting pipes, and the fittings adopt the double flange structure. This connection and combination mode integrates the merits of the A-type structure, such as high connection strength and easy installation; in addition, due to the use of the W-type straight pipes, the material costs are reduced; coupled with the compact design structure of the B type pipes and fittings, they can save more spaces than the A-type pipes and fittings.