We report here the studies of electron spin resonance (ESR) and its related defect states in doped nanocrystalline silicon films (nc-Si∶H). The samples used, which was prepared by plasma enhanced CVD method, are of two phases in structure, i. e., nanocrystallites embedded in the amorphous matrix. For phosphorus doped nc-Si∶H samples, the measured ESR g-values are 1.9990—1.9991, the line width ΔHpp(40—42)×10-4T, and the ESR density Nss is of order of 1017cm-3. For boron doped nc-Si∶H samples, the measured ESR g-values are 2.0076—2.0078, ΔHpp is about 18×10-4T, and Nss is of order of 1016cm-3. Considering the micro-structural and conducting characteristics of these kinds of films, we discuss and give explanations to the ESR sources, their ΔHpp and Nss as well. We ascribe the ESR signals in phosphorus doped nc-Si∶H to the unpaired electrons in the high density defect states located in the interfaces of nanocrystallites/amorphous matrix , and that in boron doped ones to the unpaired electrons in the valence band-tail states in the a-Si∶H tissue of their amorphous matrix.