The $16 billion dollar cancellation by the Dubai-based airline is a "credit positive" development for Airbus rival Boeing Co, the ratings agency said.
Moody's said the decision suggested more clearly the preference of at least one leading airline operating in the rapidly growing Middle East market for the Boeing 777X over the competing A350 XWB offering from Airbus.
Read MoreAirbus says Emirates cancels order
The surprise decision by Emirates to cancel all of the A350s it had on order comes just months before the long-haul jet is due to enter service.
The move removed 9 percent of the order backlog for a plane which took eight years and $15 billion to develop.
"While the cancellation immediately trims the backlogs of the affected companies (Airbus and Rolls-Royce), we believe it will not necessarily be accompanied by a big financial hit and will in fact be overcome in due course as other carriers happily move up in the production line and new orders fill the vacated slots," Russell Solomon, Moody's senior vice president, said in a report on Thursday.