Power grid inspection is an effective means to ensure the safe and stable operation of power systems, as it can promptly identify various hidden dangers and defects in power equipment. Unmanned aerial vehicle (UAV) inspection of power grids is not affected by geographical constraints and offers advantages such as high flexibility, efficiency, and low cost, effectively addressing the challenges of manual inspections, which include high difficulty, low efficiency, and high risk. However, due to the power and load limitations of UAV, it cannot carry multiple sensor devices simultaneously for inspections. This paper discusses the application of integrated sensing and communication (ISAC) technology in UAV, enabling it to perform both communication and sensing functions with a single hardware setup. Focusing on the scenario of power grid inspection, this paper proposes a joint optimization scheme for UAV trajectory and beamforming based on ISAC, aiming to maximize sensing performance while ensuring the signal-to-interference-plus-noise ratio (SINR) requirements for communication users. The numerical results show that under the same SINR threshold constraints, the average directional gain of the UAV communication beam is consistent with, or even superior to, that of the radar beam.