In order to find a more reasonable supporting structure form for ultra-high wind turbine towers in the low-wind-speed area, a type of composite structure - “inserted Lattice wind turbine tower” is originally proposed, installed capacity of 4.5 MW and a hub height of 181.7 m. The upper part continues to use the existing single-tube tower tube, and the lower part adopts the frame tower. The upper part of its support structure continues to use the existing single-tube tower tube, and the lower part is changed to adopt the Lattice tower. The structural form of the inserted transition piece is that the single-tube tower tube is inserted into the lower tower to a set depth and the tower tube is supported and connected through construction measures, meanwhile, prestressing strands are arranged in the tower columns; The stress, deformation and buckling of the entire tower are calculated and analyzed in SAP2000.The finite element analysis of the ultimate bearing capacity and fatigue performance of the inserted transition piece at the key joints of the structure is carried out in ABAQUS. The analysis results show that the arrangement of the tower with the inserted transition piece is reasonable; the overall integrity is good; the force transmission is clear; the transition piece joint design is safe and reliable, and meets the design requirements.