Abstract: Build-up pig with flexible shaft, consisting of a flexible shaft, purging cup, bushing, sealing cup and tail cup holder, is suitable for gas-liquid separation, products interface separation and pipeline pigging. The three kinds of pigs available in China, spherical, flexible shaft-integral and stiff shaft-build up pigs are analysed in detail and compared in their ways of separation, pigging and trafficability. Presented are the conception of build-up pig with flexible shaft and its features of structural design. It is concluded through theoretical by broad coverage, high practicability, comprehensiveness, and multiple ettective tactors. Supervision basis is presented according to the specifications for technical supervision of construction. Supervision engmeers carry out the following activities during construction: ① Check and verify relavent documents and report; ② Supervise and inspect construction quality, including prestart-up mspecuon, procedure handover mspection subtle project inspection, restart-up after stop inspection etc.Quality evaluation and acceptance of the project are usally carried out following the procedure of line-item project, partitioned project and unit project.Unqualified projects will not be accepted. Acceptable projects are classified into two grades: qualified and excellent. To achieve accurate, subjective and reliable result, the Fuzzy evaluation method can be used to replace the troditional Scoring Table method.