In the laser direct writing lithography system, the focus locking performance is one of the key factors affecting the exposure uniformity of the system. The dynamic response characteristics of a piezoelectric ceramic as the focus locking actuator of the lithography system are studied, and their influences on the exposure uniformity of the polar coordinate lithography system are explored. In the process of exploration, the nonlinear relationship between the dynamic response of piezoelectric ceramics to general anharmonic signals and that to characteristic harmonic signals is found, and the correctness of the relationship is verified by sample exposure experiments. Based on the relationship, the fastest working speed of the rotary table that can meet the focus locking requirements is quantitatively calculated. At the same time, the guidance for the piezoelectric ceramic manufacturers to optimize the dynamic response characteristics of the piezoelectric ceramics suitable for the polar coordinate lithography system is provided. The focus locking ability of the optimized piezoelectric ceramics is increased by 125.2%.