Complicated formation and well depth over 7000m in the piedmont region of Tarim Oilfield, China, lead to frequent tripping and more downhole accidents, and all of them cause the well construction period and costs increased significantly. 9000m quadruple stand ultra-deep well drilling rig was developed to solve the above problems. The quadruple stand rig derrick was firstly modeled with 3D design software, and then ANSYS was applied to the dynamic analysis of the derrick, including modal analysis, harmonic response and transient response. The analysis results show that the displacement in the front derrick opening direction of the crane, racking board and auxiliary racking board position is greater than the displacement in the direction of the derrick on both sides, and the low frequency forward derrick deformation should be pay more attention. The little displacement of the A-frame means that derrick will not produce large forced vibration in the process of drilling. The response displacement of the racking board is the largest and the response time is the longest under the action of transient impact load, so it is necessary to strengthen its support. The dynamic analysis provides the basis for the optimization design, strength checking and safety assessment of the derrick of quadruple stand rig.