On returning home, Dorian notices that the portrait has changed; his wish has come true, and the man in the portrait bears a subtle sneer of cruelty. ... In anger, Dorian blames his fate on Basil and stabs him to death.

How Dorian Gray dies?

By Oscar Wilde

He slashes at it with a knife (appropriately the very same knife with which he murdered his ex-friend, Basil Hallward), hoping to do away with the evidence of his crimes. But the plan backfires dramatically: by stabbing the portrait, Dorian inadvertently kills himself.

How did Dorian Gray lose his innocence?

Basil believes that Dorian's outer beauty reflects his inner goodness. Hedonism'. This, together with Basil's portrait – which encourages Dorian's narcissism and prompts him to wish he could remain forever young and attractive – initiates Dorian's loss of innocence.