The finite-time difference method is used to simulate the influence of the concave and convex defects on the edge of the antenna on the response characteristics and electric field distribution of the strip antenna on the silicon substrate. The calculation results show that both types of defects change the electric field direction and electric field strength near the defect. The convex defect can enhance the electric field in the vicinity, while the concave defect is opposite, and the closer to the end of the antenna, the stronger the effect of defects. Defects of different positions and sizes have different effects on the area of the electric field enhancement. When the concave-defect is located at the end of the antenna, as the size increases, the area where the electric field strength is increased by 2 times monotonously decreases, and the area where the electric field is enhanced by 4 times monotonously increases. When the defect is 20 nm, the area where the electric field strength is increased by 2 times is reduced by about 3%, and the area where the electric field is enhanced by 4 times is increased by about 4%. Different from the concave defect, the convex defect has no simple monotonicity, and the defect position is different, and the influence is also different. However, controlling defects within 10 nm can significantly reduce the impact. This result provides a theoretical basis for the accuracy requirements of optical antenna processing.