A synthesis method of high-speed finite state machines (FSMs) in field programmable gate arrays (FPGAs) based on LUT (Look Up Table) by internal state splitting is offered. The method can be easily included in designing the flow of digital systems in FPGA. Estimations of the number of LUT levels are presented for an implementation of FSM transition functions in the case of sequential and parallel decomposition. Split algorithms of FSM internal states for the synthesis of high-speed FSMs are described. The experimental results showed a high efficiency of the offered method. FSM performance increases by 1.52 times on occasion. In conclusion, the experimental results were considered, and prospective directions for designing high-speed FSMs are specified.