A series of original pyrimidinamine derivatives containing a biphenyl ether moiety were designed and synthesized. Their structures were confirmed by 1H NMR, MS, and elemental analyses. Their insecticidal activities against lepidopteran and hemiptera insects and acaricidal activities were tested. The results of bioassay demonstrated that 9k showed the best activity (LC50 = 2.08 mg/L) against Tetranychus urticae, which is comparable with the positive control, spirotetramat (LC50 = 2.27 mg/L), and 9g showed better activity (LC50 = 0.52 mg/L) against Aphis fabae than the positive control, imidacloprid (LC50 = 1.02 mg/L), and relatively good activity (LC50 = 2.49 mg/L) against T urticae. Their structure‐activity relationships indicated that both an ethyl group on the 4‐position of the pyrimidine ring and alkyl chain as a para‐substituent group of the benzene ring showed good biological activity.