The self-parking system is an important component of self-driving vehicles. Such a system needs to detect and locate the parking-slots from surround-view images, and then guide the vehicle to the designated parking-slot. In the real world, the appearances and environmental conditions of parking-slots can be rich and varied. Thus, to train the parking-slot detection model, it is necessary to collect and label a huge quantity of surround-view images covering as many real cases as possible. Such a process is cumbersome and costly, and will be repeated whenever encountering an unseen parking condition that is quite different from the ones covered by existing training set. To this end, in this paper we propose an extensible pipeline, namely FakePS, to assist parking-slot detection model training by making use of synthetic data. Specifically, with FakePS, we can first build various simulated parking scenes and collect labeled surround-view images automatically. Besides, we resort to pixel-level domain adaptation strategies to enhance the realism of the synthetic images using unlabeled real images while preserving their label information. The efficacy of FakePS has been corroborated by experimental results.