Problem statement: The effects of suction/injection and variable chemical reaction on mass transfer characteristics over unsteady stretching surface embedded in porous medium are studied. Approach: The governing time dependent boundary layer equations are transformed to ordinary differential equations containing chemical reaction parameter, unsteadiness parameter, and Schmidt number. These equations are solved through applying symbolic computation to Runge-Kutta technique in order to solve a two point boundary value problem. Results: The velocity and the Concentration profiles are computed and discussed in details for various values of the different parameters. Comparison of the obtained numerical results is made with previously published results. Conclusion: it found that, the velocity as well as concentration decreases with increasing the permeability parameter (λ), suction/injection parameter (fw), and unsteadiness parameter (A). and the concentration decreases with increasing the chemical reaction parameter (L) while the velocity has negligible change specially at low rate of chemical reaction .