According to the Catechism of the Catholic Church, the crucifix is a sacramental, a "sacred sign" instituted by the church that prepares Catholics to receive God's grace. For example, Catholics believe that gazing at the crucifix during prayer will help stimulate feelings of hope, love, and trust. According to the catechism, a sacramental draws its power from the paschal mystery which is central to the Catholic faith and refers to Jesus' suffering, death, and resurrection.
Source:
1) Adams, A.Why Does the Catholic Church Use a Crucifix?
2)The Vatican: Catechism of the Catholic Church