In view of characteristics of floating roof structure of 10×104m3 double disc floating roof crude oil tank， described is the importance of floating roof plate assembly quality and analyzed are reasons affecting floating roof plate assembly flatness from such two issues as design and construction. For such large-scale steel structure constituents， welding stress is the main reason of welding deformation. Combined with actual engineering practices， optimized are floating roof plate welding procedure and construction process for floating roof plate assembly of 10×104m3 double disc floating roof crude oil tank， welding stress is improved， welding deformation is controlled efficiently and double disc floating roof plate assembly quality is obviously improved. Practice has proved that the improved welding sequence is more reasonable than traditional ones.