Based on the broad-area vertical cavity semiconductor optical amplifiers (VCSOA) of 970 nm, the amplifier gain and bandwidth characteristics were experimentally investigated and analyzed in the reflection mode. For 970 nm broad-area VCSOA operated in reflective mode, the maximum gain amplification of 24.8 dB and optical bandwidth of 0.14 nm (25 GHz) were reached when the injection current was 57% of threshold current and the signal input power was 0.7 W. The experimental gain value was larger than the theoretical value, due to many modes existing in VCSOA. Each mode had relative gain amplification, so the experimental gain value was larger than the theoretical value. This kind of broad-area VCSOA was improved not only in optical gain but also in saturated input power. The authors optimized the structure design of the wide area VCSOA of 970 nm. The simulation results showed that the improvement of the gain and bandwidth of the semiconductor laser could be obtained by appropriately reducing the DBR reflectivity of the emitting laser on the vertical cavity surface.