Characteristics of Er3+-doped amplifier based on Bragg fiber with high index core are investigated. Small signal gain and noise figure are measured for forward pump configuration and backward pump configuration. The results show that, compared with conventional Er3+-doped fiber amplifier, Bragg fiber amplifier has similar amplified spontaneous emission but lower gain. With the simulation on mode field of doped Bragg fiber, the result is discussed and improving method is proposed. Moreover, characteristics of saturated gain are also studied. It is shown that Bragg fiber amplifier has larger input-dynamic-range and has potential application in automatic gain control.