A light emitting diode illuminator includes at least one light source, a receiving seat and a power source arranged on the receiving seat for supplying currents to the at least one light source for causing the at least one light source emitting light. The receiving seat includes a panel and a back plate assembled to the panel. At least one receiving chamber is defined between the panel and the back plate. The receiving chamber defines an opening at a lateral side of the receiving seat. The at least one light source is mounted into the at least one receiving chamber via the opening of the receiving chamber. A block extends outwardly from the back plate to the opening of the receiving chamber to prevent the at least one light source from falling out from the at least one receiving chamber of the receiving seat.