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