The Structural, electronic and chemical bonding of the Sn doped PbX (X=S, Se, Te) are calculated by full potential linearized augmented plane wave method (FP-LAPW) within density functional theory (DFT). Generalized gradient approximation of Wu and Cohen (WC-GGA) is used for calculating the exchange correlation effects. The structural parameters changes with respect to doping. The calculations show that the band gap decreases with the increase of Sn concentration. It has observed that the s, p and d states of PbX (X=S, Se, Te) control their electronic properties. The alloys Pb1–xSnxS, Pb1–xSnxSe and Pb1–xSnxTe show covalent bonding nature which enhances by increasing the Sn concentration.