Abstract: A field population of seven-spot ladybird, Coccinella Septempunctata Linnaeus, was selected for imidacloprid resistance under laboratory condition to explore the resistant developmental dynamics. After 20 generations, the selected population showed resistance increase of 63.1519 folds compared with that of a susceptible strain. Biological characteristics were also investigated in three groups of C. septempunctata, the resistant strain (R), the susceptible strain (S) and a field population (F). Significant difference was observed in the larval duration among the three groups, larval stage of R, S, and F were 12.36 days, 10.62 days and 9.88 days, respectively. No differences were found in pupal duration. There was slight difference among the three groups in body weights of the 4th instar larvae as well as pupae and male adults. Egg hatching rates were 63.0%, 62.4%, and 66.3% in the prophase, respectively; 64.8%, 58.7%, and 75.6% in the midphase, respectively; and 69.3%, 57.4%, and 75.5% in the anaphase, respectively; with no significant difference among groups. Average fecundity were 1043.3, 1100.2, and 1250.1 eggs per female, respectively, there was also no significant difference. The results indicate that resistance to imidacloprid had only marginal influence on biological fitness of C. septempunctata.