Dengue Hemorrhagic Fever (DHF) is a public health problem in Indonesia. Port Health Office Class II Semarang as an institution which has the task of eradication of dengue, vector control stressing that Ae.aegypti mosquitoes through fogging. They do fogging activities 3 months although no cases. Using of insecticides in a long time cause resistance. Resistance of insect to organophosphate increased non-specific esterase enzyme activity were tested by mikroplate assay. This study aims to determine the resistance status of Ae. aegypti in the perimeter and buffer based on susceptibility testing and see the activity of detoxifying enzymes using biochemical tests. This research used experimental method to study design posttest only control group. The samples using 25 mosquitoes with four replications based on WHO standards and 30 mosquitoes for biochemical tests. From this study showed that the percentage of mosquitoes origin Buffer death by 13% while the Perimeter by 20%. Based on chi square test not found significant difference between the number of mosquitoes susceptible, medium resistant and high resistance between the region of Perimeter and Buffer (p> 0.05) with a high proportion of resistant mosquitoes is 83.3%, while in the Buffer is 66.7%. They need rotation insecticides for mosquito control and susceptibility test for insecticides periodically.