以假乱真

以假亂真
yǐjiǎluànzhēn
(idiom) to pass off the fake as genuine; to blur the line between fake and real so convincingly that the fake is mistaken for the real thing

CEDICT

拿假的冒充真的，使真假不分

維基詞典

Entry Composition

=1 以 yǐ old variant of 以 yǐ
=1 以 yǐ old variant of 以 yǐ
=1 以 yǐ
  1. to use
  2. by means of
  3. according to
  4. in order to
  5. because of
  6. at (a certain date or place)
=2 假 jiǎ
  1. fake
  2. false
  3. artificial
  4. to borrow
  5. if
  6. suppose
=2 假 jiǎ
  1. variant of 假 jiǎ
  2. to borrow
3 乱真 luànzhēn
  1. to pass off as genuine
  2. spurious