How st Jude become saint?

Since St. Jude died as a martyr, beaten to death and then beheaded, the early Christians declared him a saint based on the martyrdom he endured.
St. Jude earned is sainthood by dying as a martyr for his faith. There was no formal process for canonization in place at the time. He was declared a saint by general acclamation soon after his death in the first century.
Catholic tradition holds that Saint Jude was martyred because of his faith in Christ around the year 65 A.D. in Persia (modern-day Iran). Christians who gave their lives for Christ were, after their deaths, nearly always revered as saints by the Church of antiquity.