The invention relates to a servo motion control device based on a floating-point DSP, which comprises a DSP unit circuit, a power circuit, a program memory circuit, a dual-port RAM circuit, a PC104 bus interface circuit, a board election control circuit, an orthogonal counter circuit, an I/O port expansion circuit, a servo interface circuit and a serial port control circuit. The invention can realize the high-precision motion control of the AC servo motor with the photoelectric encoder as the feedback through the software based on the floating-point DSP, including the angular position, angular rate, angular vibration and other motion modes, and not only can be used as the expansion board of the PC104 bus, but also can be used as the independent motion controller. Moreover, the invention has the advantages of high performance of real-time control, high flexibility of expansion and high control accuracy of the control system, and can be applied in the turntable system and servo platform of the field of the inertial navigation testing equipment and other fields requiring the accurate control of angular motion such as robots and the like.