Abstract: Allene-like and cumulene-like oligomers with two CH2 groups at both ends of the oligomers ( H2CnH2 ) have been found to give helical molecular orbitals for HOMO and LUMO and around the MOs when two CH2 groups are tilted from their equilibrium position. This result can be explained due to the change of the symmetry for H2C2m+1H2 from D2d to D2 , the former has degenerate molecular orbitals but latter has non-degenerate ones. This helical molecular orbitals have been pointed out to be a kind of molecular devices when electrons are going through these helical orbitals. In order to obtain stable tilted polyyne oligomers, appropriate environmental design around the oligomers should be needed. Preliminary tentative calculations indicate that this is possible.