We calculate all high energy string scattering amplitudes in both the fixed angle and Regge regime.In the fixed angle regime,we discover an infinite number of linear relations and ratios among scattering amplitudes of different string states,and thus prove the conjecture on symmetries of string by Gross in 1988.In the Regge regime,we show that all scattering amplitudes can be expressed in terms of generalized Kummer functions of the second kind.Finally we prove a set of identities based on signless Stirling number in combinatorial theory to link these two set of high energy string scattering amplitudes.