  We calculate the thermal correction to the entanglement spectrum for
separating a single interval of two dimensional conformal field theories. Our
derivation is a direct extension of the thermal correction to the R\'enyi
entropy. Within a low-temperature expansion by including only the first excited
state in the thermal density matrix, we approach analytical results of the
thermal correction to the entanglement spectrum at both of the small and large
interval limit. We find the temperature correction reduces the large
eigenvalues in the entanglement spectrum while increases the small eigenvalues
in the entanglement spectrum, leading to an overall crossover changing pattern
of the entanglement spectrum. Crucially, at low-temperature limit, the thermal
corrections are dominated by the first excited state and depend on its scaling
dimension $\Delta$ and degeneracy $g$. This opens an avenue to extract
universal information of underlying conformal data via the thermal entanglement
spectrum. All of these analytical computation is supported from numerical
simulations using 1+1 dimensional free fermion. Finally, we extend our
calculation to resolve the thermal correction to the symmetry-resolved
entanglement spectrum.
