The present disclosure relates to a collimator. The collimator may include a motor, a transmission unit having a first end and a second end, and a leaf unit having a leaf. The first end of the transmission unit may be connected to the motor and the second end of the transmission unit may be connected to the leaf. The present disclosure also relates to a collimator system. The collimator system may include a leaf module having a leaf, a driving module having a motor configured to drive the leaf, and a processing module to generate a movement profile of the leaf. The movement profile of the leaf may include a first speed during a first stage, a second speed of the leaf during a second stage, and a third speed of the leaf during a third stage.