A portable electronic device (20) comprises a housing (22), a battery (26), a battery cover (28) and a trigger mechanism (24). The housing (22) have a battery chamber (222) defined therein. The battery cover (28) have a mating portion (2822) formed thereon. The battery (268) assembled in the battery chamber (222) with the battery cover (28) covering thereon. and The trigger mechanism (24) comprise an expanding portion (242), a securing portion (244), and a resisting portion (246), the securing portion (244) have two ends respectively connecting the expanding portion (242) and the resisting portion (246), the mating portion (2822) is configured for securely engaging with the securing portion (244) so as to restrain the expanding portion from expanding. The expanding portion (242) is secured within the battery chamber (222). The resisting portion (246) is configured for resisting against the battery (26). When the mating portion (2822) disengages from the securing portion (244), the expanding portion (242) expands and the resisting portion (246) ejects the battery (26) from the battery chamber (222).