We demonstrated the first circularly polarized luminescence (CPL) and circular dichroism (CD) spectra of three new Si-Si-bonded network polymers bearing the chiral alkyl side groups poly[(S)-2-methylbutylsilyne] (1S), poly[(R)-3,7-dimethyloctylsilyne] (2R), poly[(S)-3,7-dimethyloctylsilyne (2s), and, For comparison, poly(n-pentylsilyne). which bears an achiral alkyl side group (3). These polymers were successfully prepared by Na-mediated condensation of the corresponding alkyltrichlorosilanes with thee help of crown ether It was revealed that only 1S. which bears a beta-branched chiral group, clearly showed an intense CPL signal at similar to 570 nm with a quantum yield of similar to 1%, along with its corresponding Cotton CID signals in tetrahydrofuran at room temperature. In contrast. 2R and 2S, which possess gamma-branched chiral garoups, did not show any CPL signal. though they did show the CID bands As expected. 3 did not show CPL or CD signals The beta-branched chiral side chain was needed to provide the intense CPL band in the visible region and to effectively induce chirally distorted Si-Si-bonded structures in Si-Si-bonded network polymers