Lee, winner of four BWF Superseries tournaments this season, was on court for just 40 minutes as he overcame sixth seed Wang Zhengming 21-8 21-11 in Copenhagen on Friday.
The Olympic silver medalist at London 2012 was particularly dominant in the first game, winning eight straight points from 13-8.
Wang fared little better in the second game, as Lee romped to victory to set up a semi-final showdown with home favourite Viktor Axelsen, who continued his fine run with a straightforward 21-14 21-14 victory over Chou Tien-chen.
On the other side of the draw, second seed Chen continued his quest for a final berth but was taken the distance in a tight encounter with seventh seed Son Wan-ho.
Having won the opening game 21-14, Chen surrendered the second before recovering from a losing position in the decider to clinch a 21-14 12-21 21-17 triumph.
Awaiting in the final four is Tommy Sugiarto, seeded fifth, who overcame Eric Pang 22-20 21-19.
In the women's draw, the top-ranked Li Xuerui recorded a comfortable a 21-15 21-15 success over Saina Nehwal and will next meet 16th seed Minatsu Mitani, who shocked Sung Ji-hyun in a come-from-behind victory.
Second seed Wang Shixian was also a surprise casualty; she took the first game in her encounter with PV Sindhu but was eventually ousted 19-21 21-19 21-15.
Carolina Marin makes up the semi-final quartet. The Spaniard also needed three games to beat Tai Tzu-ying.