After Chongqing has become the municipality directly under the central government, it develops fast and the electric power consumption increases dramatically. The construction of 110 kV ca- bles also speeds up. In cable transmission, the load can not exceed the permissible ampacity, or the cable will overheat and cause accidents or reduce its service life. The paper has adopted the finite ele- ment method to calculate the temperature field distribution of the 110kV 800mm2 YJLW02 in different laying patterns and applied two-point secant method to calculate the current-carrying capacity. The result shows that the temperature of the cable core for installation in tunnel is the lowest, which is helpful to reduce the cable temperature, prolong its service life and increase its efficiency.