A novel ice monitoring system for the overhead transmission lines based on fiber Bragg grating (FBG) sensing is proposed in this paper. Compared to the existing systems, this system has several unique advantages, such as unnecessary power supply onsite, excellent ability for avoiding electromagnetic interference, and long lifespan. First, two near-elliptical-shaped concavities with FBG in each side are designed on the column structure to improve accuracy in measuring eccentric load. Then, a high reliability and high resolution tilt sensing section is developed based on a beam of uniform strength where an FBG is fixed on. Finally, an unforced FBG is placed in the sensor to solve the cross-sensitivity of strain and temperature in FBG sensing. Tension and angle experiments are conducted in our laboratory to calibrate the sensor. The tension experiment results indicate that the sensor is sensitive to tension, and the sensitivity and resolution of the sensor are 0.0413 pm/N and 24.21 N. The results of the tilt angle experiment show that the sensitivity and resolution of the sensor is 16.17 pm/° and 0.0619°. The temperature effect on the tension and angle measurement, evaluated by putting the sensor in an oven, is less than ±0.3% and ±0.38% separately. A 250-h outdoor experiment was carried out in the testing field, and the results prove the sensor can work properly in harsh environments and no creep is observed during the experiment.