Abstarct: As one of the geophysical methods, Gravity is used on the basis of difference between the density of the studied structure and the field of surrounding environment in discoveries (including blank spaces and cavities). Aqueduct and gas pipeline buried underground can be identified by using gravity surveys because of creating empty space underground and failure zones. But in order to better identification, microgravity (small areas and adjacent areas) can be used. Assessment of gravity operation has been carried out in northwestern Damghan on Haji Abad aqueduct. Picking up zone was chosen so that either one of vertical bars of aqueduct and gas pipeline (crossing above aqueduct) were included in the picked network. Thus the 8 North - South direction profile perpendicular to the aqueduct strike was designed and 550 gravity stations were measured. After performing different corrections including drift and tide, latitude, free air, bouguer correction, and topography, relative gravity anomalies were calculated. Different methods and filters have been applied for processing of data. Buried gas pipeline and vertical bars of aqueduct are seen in final mapping, but it is difficult to detect the horizontal channel of aqueduct well which was located at the depth of 15 meters. Also, the failure zones of old aqueduct located adjacent and it is gravity effect is higher than to new ones. The network design requires that we somehow picked to model by synthetic structure to achieve convincing results. Therefore, the horizontal channel of aqueduct, vertical bar of aqueduct and gas pipeline were modeled by three cylinders according to the information related to exploratory area. Modeling results indicate that network design (especially in microgravity) is one of important parameters for achieving the target and affect on the final results. Other research results that were achieved in the present study are the stronger effects of surface structure related to the deep structures that will remove their effects in output map. Also, identifying and detecting failure zones of an old aqueduct along with gravimetric survey were almost feasible.