It's important to simulate micro hard disk read-write channel servo signal for design and test. This paper researChes a programmable signal generator by an improved high integrated direct digital frequency synthesis (DDFS) technology to simulate servo signal for read-write channel of micro hard disk. This device use very large-scale integrated cirCuit FPGA (field-programmable logic) to integrate high speed PDSP (programmable digital signal processor) design and DDFS design. Test results indicate that this device has higher precision and sequence of signal, and the cirCuit need not connect filter and can output 2-512 order harmonious. The cirCuit design is simply, reLiable, and programmable, compared with general design by separate parts design.