The performances of high power Er/Yb codoped fiber linear cavity lasers are investigated numerically. The numerical analysis is based on the iterative solution of rate equations for population density of the Er/Yb ions. The behaviors of co-pump and counter-pump methods are contrasted. Dependence of output power on input pump power,output reflectivity, operating wavelength and active fiber length is simulated,respectively. High conversion efficiency Er/Yb laser output is obtained in simulations and experiments.