Abstract: A high reliability dual power sources automatic switch circuit and an isolation apparatus thereof are provided. The dual power sources automatic switch circuit includes a main power source circuit and a backup power source circuit installed respectively in a main circuit automatic switch zone and a backup circuit automatic switch zone which are isolated by a main isolation board in the isolation apparatus. The main and backup power source circuits include manual switches installed in a manual switch zone isolated by a sub-isolation board. The main power source circuit includes a main switch which includes multiple main switch elements coupled in series. The backup power source circuit includes a backup switch which includes multiple backup switch elements coupled in parallel. The invention also includes a power monitor module to monitor abnormal conditions of the main and backup power source circuits, and control the switch elements to perform power supply transfer.