An assembly system, comprising: a robot adapted to grip an electronic device to be mounted on a circuit board; a first vision system configured to identify a position and a posture of the electronic device gripped by the robot; a fixing device adapted to fix a plurality of circuit boards thereon; and a second vision system configured to identify a position and a posture of the circuit board fixed on the fixing device, wherein the robot is adapted to mount the gripped electronic device on the circuit board under the visual guidance of the first vision system and the second vision system, and a view field of the second vision system, when the plurality of circuit boards is fixed on the fixing device, is not capable of completely covering a surface region of all circuit boards fixed on the fixing device; and wherein the assembly system further comprises a moving mechanism (210, 220) adapted to move the second vision system in a first horizontal direction and a second horizontal direction perpendicular to the first horizontal direction, so that the second vision system completes identification of all circuit boards on the fixing device step by step, characterized in that the assembly system further comprises a rotatable table on which a plurality of fixing devices are mounted, wherein the plurality of fixing devices are arranged around the periphery of rotatable table and separated from each other, wherein the rotatable table is adapted to rotate the plurality of fixing devices in turn to an assembling station where the robot performs an assembly work of mounting electronic devices on the circuit boards fixed on one fixing device. a robot adapted to grip an electronic device to be mounted on a circuit board; a first vision system configured to identify a position and a posture of the electronic device gripped by the robot; a fixing device adapted to fix a plurality of circuit boards thereon; and a second vision system configured to identify a position and a posture of the circuit board fixed on the fixing device, wherein the robot is adapted to mount the gripped electronic device on the circuit board under the visual guidance of the first vision system and the second vision system, and a view field of the second vision system, when the plurality of circuit boards is fixed on the fixing device, is not capable of completely covering a surface region of all circuit boards fixed on the fixing device; and wherein the assembly system further comprises a moving mechanism (210, 220) adapted to move the second vision system in a first horizontal direction and a second horizontal direction perpendicular to the first horizontal direction, so that the second vision system completes identification of all circuit boards on the fixing device step by step, characterized in that the assembly system further comprises a rotatable table on which a plurality of fixing devices are mounted, wherein the plurality of fixing devices are arranged around the periphery of rotatable table and separated from each other, wherein the rotatable table is adapted to rotate the plurality of fixing devices in turn to an assembling station where the robot performs an assembly work of mounting electronic devices on the circuit boards fixed on one fixing device.