The low intensity focused ultrasound treatment technology is a research hotspot in the field of ultrasound treatment. Different application scenarios have different requirements for parameters and performance of the ultrasound system, while the introduction of phased array technology brings new ideas to solve the problem of accurate control of the focused sound field. The output parameters of the existing phased array focused ultrasound control system are relatively fixed, the adjustable range of frequency and power is narrow, and the scale of supporting the transducer array channel is small. This paper presents a 256 channels phased array ultrasound control system based on FPGA. The experimental results show that the frequency of the system can be adjusted from 1 MHz to 3 MHz, the peak to peak value of the voltage is continuously adjustable within ±100 V, and the control precision of phase controlled delay is 5 ns. It can drive phased array probes with different array elements, so as to provide diversified incentive schemes for the research of ultrasonic therapy technology.