A novel Yb∶YAG surface gain slab laser amplifier is designed, with a fiber laser seed, using the geometry of master oscillator power amplifier (MOPA). Single-pass and double-pass amplifying are investigated theoretically and experimentally. The results show that 1030 nm laser output is obtained at room temperature. Under the conditions that the total pumping power is 11.2 kW and the injected power of fiber seed laser is 200 W, the output power of single and double pass amplified laser are 1.6 kW and 2.6 kW, respectively, and the optical efficiency of the two methods are 12.8% and 21.4%, respectively. The transmission wavefront of Yb∶YAG surface gain slab is measured and the wavefront distortion value is 1.3 μm. Yb∶YAG surface gain slabs have the potential as gain medium of high power lasers.