Objective To establish the relative susceptibility baselines and diagnostic doses of the wild population of Haemaphysalis longicornis to common insecticides. Methods The wild population of H. longicornis without exposure to any pesticides was collected at Mount Wangwu in Henan, China from April to September in both 2013 and 2014. The residual film method was used to determine the susceptibility of adult H. longicornis to insecticides. DPS data processing software was used for probit analysis, and the toxicity regression equation was fitted to determine the median lethal dose and 99% lethal dose and then to calculate the diagnostic dose. Results The susceptibility baselines of H. longicornis to dichlorvos, temephos, bassa, permethrin, deltamethrin, and beta-cypermethrin were y=1.549 9+1.359 4x, y=2.343 3+1.225 6x, y=-6.850 7+5.213 9x, y=0.866 1+1.571 1x, y=0.411 6+2.277 8x, and y=2.551 8+1.018 9x, respectively; the diagnostic doses were 35.505 6, 10.764 7, 1.047 4, 25.872 9, 2.171 4, and 97.063 2 mg/L, respectively. Conclusion The relative susceptibility baselines of the wild population of H. longicornis to the six insecticides, as well as the diagnostic doses, have been established. The results can be used as a reference for monitoring the resistance of H. longicornis to pesticides.