The interaction on and the rotation of C,, in akali-doped C,, solids, A,A!-,C,, (X = 1,2,3; A, A' = alkali), have been calculated with Buckingham potential model. The results show that the total interaction on C,, changes dramatically when the pure C,, solid is alkali-doped into K,C,,. The interaction on C,, in K,C,, is about 20 times greater than that in pure C,,. And the main component in the former, occupying > 90% is electrostatic, while in the latter, the main components, occupying > 90%, are dispersive and repulsive. The results also show that in contrast to the whole-region free rapid rotation of C,, molecule in its pure solid, the rotation of C, in K,C,, is mostly forbidden due to a 10 times increase (reaching about 300 kJ/mol) in potential barrier, except for the region from 0" to 50" where a broad, smooth, and shallow potential well exists. Calculations for alkali-doped complexes other than K,C,,, i.e., A xA',_ C,, (X = 1,2,3; A, A' = K, Rb, Cs), come to the same conclusion. Finally, an interesting and meaningful result is that the superconducting transition temperatures of A xA',_ C,, (X = 1,2,3; A, A' = K, Rb, Cs) change inversely with the total interactions on C, .