The mechanical behavior of transmission towers and the maximum jump height of conductors following ice-shedding are critical factors in tower head design. In ultra-heavy ice zones, ice thickness on ultra-high voltage direct current (UHV DC) line can reach 60 mm to 80 mm, exceeding the maximum values specified in current transmission line design codes. This study establishes finite element models of UHV DC tower-line systems in ultra-heavy ice zones and numerically simulates their dynamic responses under ice-shedding conditions for varying span lengths. The analysis evaluates tower stresses, longitudinal unbalanced tensions, and maximum conductor jump heights to assess both structural performance and electrical isolation clearances. Results indicate that longitudinal unbalanced tensions surpass estimates from current design codes, and maximum conductor jump heights exceed predictions from existing empirical formulas. To enhance design accuracy, the study proposes revised values for longitudinal unbalanced tensions and modifications to the conductor jump height formula.