To reduce the torsional effect of L-shaped irregular structures, this paper explores the control effect of three seismic joint design schemes for the isolation layer on torsional effect in seismic isolation design, and proposes an overall design process for L-shaped irregular structures. Based on the complex mode decomposition response spectrum method, an overall model of the upper structure isolation layer lower structure of an L-shaped building is established. The equivalent stiffness and damping ratio of the isolation device are determined through iterative calculation, and the modified response spectrum calculation is carried out; Add elastic-plastic time history analysis to the optimal solution in SAUSG, and ve-rify the ultimate displacement of the support and the displacement angle of the floor under rare earthquakes. The overall design method determines the seismic isolation target based on the bottom shear ratio and uses multiple calculation model envelopes to make seismic isolation design more intuitive and convenient. The scheme of setting vertical seismic joints was adopted to reduce the torsional displacement ratio from 1.60 to 1.16, and the displacement angle from 1/212 to 1/505, effectively controlling the torsional effect.