  The well known soft theorems state the specific factorizations of tree level
gravitational (GR) amplitudes at leading, sub-leading and sub-sub-leading
orders, with universal soft factors. For Yang-Mills (YM) amplitudes, similar
factorizations and universal soft factors are found at leading and sub-leading
orders. Then it is natural to ask if the similar factorizations and soft
factors exist at higher orders. In this note, by using transformation operators
proposed by Cheung, Shen and Wen, we reconstruct the known soft factors of YM
and GR amplitudes, and prove the nonexistence of higher order soft factor of YM
or GR amplitude which satisfies the universality.
