1. A method for evaluating similarity deviation between molecular orbitals of a molecular structure, comprising: a) selecting two molecular orbitals to be compared for molecular orbital similarity, and obtaining N x multi-block spectra (MBS) pairs by i) computing molecular orbital distributions by a quantum chemistry calculation, ii) building N blocks arranged in a radial direction from a center of the molecular structure, iii) calculating a molecular orbital ratio (BX(k)) associated with each of the blocks (k is a natural number and represents a block number ranging from 1 to N), iv) rearranging the blocks consecutively by orbital ratio (BX(k)) size, v) with an exception that blocks are built at different sizes, repeating steps ii) to iv) for individual molecular orbitals of interest to give N x MBS per molecular orbital, the MBS being different in block size, and assembling N x MBS pairs by block size; b) performing multi-step identity estimation on the N x MBS pairs to calculate total similarity score (TSS) (m) for each of the MBS pairs (m is an MBS number ranging from 1 to N x ); and c) calculating a standard deviation of TSS (m) for each of the MBS pairs, and evaluating similarity deviation between molecular orbitals on a basis of the calculated deviations.