3 omega technique is effective for the thermophysical property measurement of micro- and nanosized samples. In the present study, a new theoretical approach for the harmonic self-heating technique is presented to simultaneously measure the specific heat and thermal conductivity of thin samples. The numerical analysis of transient heat-conduction equation and a virtual lock-in amplifier are combined to substitute the traditional analytical expression. This approach is capable of providing a more general insight into the harmonic signals at different desired frequencies such as 2 omega signals, which are also informative to extract thermophysical properties such as the traditional 3 omega technique, as well as to be readily extended to more complicated experimental configurations in terms of the advantage of numerical calculation. A suspended microsized platinum wire is first studied to confirm this theoretical approach. In further, 2 omega and 3 omega techniques based on the present theoretical approach are also used to measure the thermal conductivity and specific heat of a single carbon fiber. (C) 2009 American Vacuum Society. [DOI: 10.1116/1.3225602]