Individual and scattered studies on the optical properties of B-N substituted cyclocarbons of different sizes emphasize the positive effect of the B-N unit, but systematic research on the optoelectronic properties of the hybrid ring with C-C units sequentially replaced by B-N units appears not yet conducted thus far. Considering the unique optical properties of C18 and the potential regulatory role of B-N unit on the electronic structure, we believe that exploring the effects of B-N cumulative replacement on optoelectronic properties of C18 is worthy of investigation. As part of our continuous efforts towards theoretical studies over the C18 and its analogues, in this paper, we propose the use of the B-N cumulative effect to regulate the electronic, nonlinear optical, and photophysical properties of the C18. This work lays the foundation for the research of novel NLO materials based on the B-N analogues of cyclocarbons, and may provide new electronic and optical materials suitable for different requirements.