Current studies on the relationship between carrier concentration in nano-scale semiconductor structure and its local conductance is mainly on parameters fitting. For above connection, existing models rely on artificial fitting parameters such as ideal factor. For above reason, derivation of carrier concentration though measured local conductance can not be done. In this work, we present a scheme to obtain the carrier concentration in narrow quantum wells (QWs). Cross-sectional scanning spreading resistance microscopy (SSRM) provides unparalleled spatial resolution (<10 nm, Capable of characterizing single QW layer) in electrical characterization. High-resolution local conductance has been measured by SSRM on molecular beam epitaxy-grown GaAs/AlGaAs QWs cleaved surface (110). Based on our experimental set-up, a model which describes conductance by the only argument, i.e. carrier concentration has been built. Using the model, our implementation derived carrier concentration from SSRM measured local conductance in GaAs/AlGaAs QWs (doping level: 1016/cm3-1018/cm3). Relative errors of the results are within 30%.