The one-end-pumped Yb³⁺-doped gain guided and index antiguided (GG+IAG) fiber laser is analyzed with a rate equation model. By solving propagation rate equations, the pump and signal, the gain coefficients and other characteristics are obtained. Computation results show that a properly designed Yb³⁺-doped GG+IAG fiber laser can provide a large-mode laser with a short length. The most important issue addressed is the way of controlling the fiber laser length.