Abstract: A mixed frequency bioelectrical impedance measuring system based on the virtual instrument is suggested,in order to collect the bioelectrical impedance information in different frequencies,concurrently.Hardware platform of the system is composed of the signal source module,the signal conditioner and PCI-6111 card supplied by NI.Research on information extraction in the mixed frequency excitation mode and impedance measurement based on a virtual reference point is presented.Using LabVIEW,functions concerning the collection,analysis,display and recording can be implemented,which greatly improves the efficiency in development. Experimental tests in comparison with the Agilent4294A impedance analyzer showed that the precision and accuracy in detection of the system are excellent.