The first-principles pseudo-potential plane wave method is used to calcula te the geometric structure,electronic structure and optical properties of two-dimensional SiC doped by the adjacent e lements of C-Si (such as B,N,Al,P). The results show that the doped two-dimensional SiC lattice constants (a,b),bond length,and angle have changed significantly.In the forbidden band,the impurity levels are introduced,and bo th the conduction band and the valence band move to the lower energy direction,which make the band gap change.The 2p and 3p states of the impurity are introduced near the Fermi level.The calculation of optical properties shows tha t the ability to absorb electromagnetic waves of two-dimensional SiC has been enhanced obviously in the low energy rang e after (B,N,Al) doping.At the same time,the static dielectric constant increases and the peak of loss functio n decreases.The above results indicate that the optoelectronic properties of two-dimensional SiC can be modulated by d oping B,N,Al,P as required.