As one of the fundamental structures in Smartgrid concept, Microgrid has critical effort on maintaining user's power quality and efficiency therefore reduce energy consumption and carbon emission. Harmonic environment of an electric network means the characteristic of distribution of the harmonic energy, voltage and current, in the network. Harmonic environment of Microgrid is complicated due to nonlinear equipments, e.g. thyristor based power converter. The nonlinear equipments are both harmonic source and harmonic vulnerable, so that the assessment of Microgrid harmonic environment is very necessary for programming construction and operation of Microgrid. The modal analysis is able to figure out the paths harmonic spread and element effecting spread, but the method can not deal with nonlinear equipments properly, even those equipments are playing main role in harmonic problem in Microgrid. In this paper a maturity nonlinear equipment model is introduced in modal analysis for fully Microgrid harmonic assessment. According to the assessment results, proper measures can be taken place to improve the construction and operation of Microgrid. The method proposed in this paper has been approved to be rational and effective by the simulation test results.