Nonintrusive load monitoring (NILM) is an important development direction of the future load monitoring, the development of innovative service product based on NILM needs to carry out a detailed study on application base of NILM. First, the application system of NILM is established; second, the realization principle of identification algorithm in system is proposed. The study of load signatures is the foundation of NILM, the development of all kinds of innovative service product must be based on the load signature research. At last, this paper conducts the research on the microscopic signatures of the typical residential loads and builds their electrical modeling. Several microscopic signature values are extracted from measured current waveforms, such as crest factor, peak and rms values of transient power, area and slop factor of V-?I curve, etc, and the calculation method of the load signature values is proposed. Research work and achievement lay the foundation for subsequent electricity visualization research based on NILM.