Based on the heat conduction equations and the Gauss-Seidel numerical method, the distribution of temperature, thermal stress and thermally induced refractive index in partially pumped slab lasers are analyzed and comparied with single- and double-side pumped configurations. It is found that a partially pumped slab laser designed appropriately does not suffer more thermal distortion than that in the uniformly pumped ones, meanwhile maintaining high pumping efficiency. Whether the laser works in zigzag or straightforward path, good beam quality is achieved. If Gaussian beam passes the central portion of the crystal in straightforward path, the beam quality factor M2 is 1.4, while in zigzag path M2 is improved to 1.1.