Abstract: As everyone knows, systems science is a new discipline for scientificmethodology. Systems science researches the common characteristics of allcomplex systems in nature and human society, exploring the universal laws inthe generation, the evolution and the emergence of systems in general.Classical science pays attention to the reductive analysis while the systemsscience emphasizes holistic grasp, with substantial distinction inmethodology. In this paper we first review our important achievements insystems science methodology, next introduce the results in descriptionmethod using operations research, emphasizing the use of networkmodelling and analysis inthe research methods of systems science.