The partial segment assembly is very important to shield launching, and the assembly method will affect the project′s schedule, shield launching and the assembling quality of the following rings （i.e. inclination and rolling angle, etc）. The assembling steps of the partial segment of Baicheng Tunnel of MHTJ01 Bid Section on Menghua Railway are presented when shield launching; the positioning and fixing method of the segments during assembling of the partial ring are studied; and the supporting mode of the horseshoeshaped segment is designed. Finally, a suit of scientific, safe, highefficient and instructive assembling method of noncircular shield segment is developed.