We study the pseudoscalar and vector B mesons decay constants within the framework of the light cone quark model (LCQM). LCQM deals with the wave function defined on the four-dimensional space-time plane defined by $x^+ = x^0 +x^3$ and includes the important relativistic effects that are neglected in the traditional constituent quark model. With the help of known values of constituent quark masses and the scale parameter $\beta$, we calculate the values of B mesons decay constants, respectively. The decay constants of pseudoscalar and vector mesons are useful for controlling the meson semileptonic decay widths, hadronic couplings and form factors.