In developing a daylighting system, the overall system efficiency is crucial. In the daylighting system, whether the light propagates parallel strongly affects the efficiency. In this paper, we simulate a multicurvature lens to collimate rays propagated from different angles. We describe a method based on a freeform microlens array, which increases transmission efficiency. Results show that with the freeform microlens array collimator, the light propagates provide at least 50.26% parallel and the efficiency increases by 24.76%, enhancing the core values of the daylighting system in building illumination.