Two-dimensional materials attracted extensive attentions in recent years due to their unique properties and various potential applications. In this paper, based on crystal structure prediction, we acquired two stable 2D monolayers of Boron-Carbon-Phosphide compounds, a honeycomb-like and completely flat monolayer BC2P and a semiconductor-metal transition monolayer BC3P3, and discussed structural, electronic and optical properties of the monolayers. Two monolayers are indirect semiconductors having band gaps of 1.4095 (2.0176) eV and 0.4099 (1.004) eV with GGA-PBE (HSE06) which can be tuned under different tensile strains. The wide and tunable band gap of monolayer BC2P makes it exhibit more advantages in terms of high-frequency-response optoelectronic materials. Furthermore, under a-biaxial tensile strain from 6% to 9%, the monolayer BC3P3 can be transformed from a semiconductor to a metal, indicating it has potential applications in strain-engineering nanodevices.