The transmission lines generally using conductor with ACSR (Aluminium Conductor Steel Reinforced) which has limited temperature until 90 degrees. In this present time, the need of electricity is increasing rapidly; considering from that problem, we need to increase the capacity of transmission line by optimizes the capacity of line conductor from the transmission line before. The main problem of optimizing the transmission line are the tension and sagging of the conductors become bigger. Based from this situation the research is conducted to know about the characteristic of the alteration of current line to tension and sagging of the conductors. Therefore, the result of the research can be useful in designing the structure construction of transmission line which suitable to the conductor's characteristic. As a simulation model, Paiton-Krian 500 kV transmission line is used. The data, including the data of ACSR conductor, are collected from the field. The conductor's temperature is calculated using heat-balance method. Ruling Span method is used to measure the length of equivalent span. Mean while the Catenary method is used to measure the conductor's tension and sagging. In conclusion, it can be seen that the alteration of line current from 10 Ampere to 850 Ampere will cause the conductor temperature increase 125.94%, the tension decrease 36,38% and the sagging increase 26.82%.