Cristiano Ronaldo could however hit the 700th mark when they battle Ukraine on Monday as they hope to seal their qualification to the European championship next year.
Portugal are the defending champions after winning the last edition in France four years back – beating Les Blues in the final.
Manchester City winger Bernando Silva opened scoring for Fernando Santos’ side after just 16 minutes of action.
The 25-year-old benefited from a lose ball from Luxembourg’s keeper to fire a low shot from close range into the net. And that was the only goal they got in the first half of the meeting.
Ronaldo then stepped up his game in the 65th minute to double his side’s lead through a superb finish having intercepted a pass from the opponent and looped the ball beyond the keeper’s reach straight into the net.
With one minute to wrap up the game, Goncalo Guedes made it three for the European Cup defending champions.
Portugal remain second on Group B table with 11 points after five matches and they will face table toppers Ukraine on Monday.