A cloud-based test system is disclosed. The cloud-based test system utilizes several cloud systems for testing. Each cloud system includes several cloud servers for providing a cloud resource to simulate several virtual test machines. The cloud-based test system includes several slave servers and a main server. Each slave server corresponds to one of the cloud systems for controlling the corresponding virtual test machines. The main server receives a test instruction, which is utilized to execute a target test item for a target electrical device, from a client, and generates a test environment condition corresponding to the test instruction. The main server determines the virtual test machines for executing the target test item and the at least one server to control the virtual test machines. The main server transmits the test instruction and the corresponding test environment condition to the server slave servers for testing.