A quick detection algorithm based on the novel designed LED array and the connected component labeling technique is proposed and applied in image sensor based visible light communication (IS-VLC) system. Inspired by the Quick Response (QR) code design, the four corner LEDs on the array are defined as flag LEDs and three of them maintain on status all the time. A novel method to recognize flag LEDs by searching an isosceles triangle with the largest area is also proposed. By means of recognizing the flag LEDs, the proposed algorithm is able to detect and extract the LED array from the background quickly even though relative rotation exists between the LED array and an image sensor, which is particularly suitable for the LED-ID applications such as indoor positioning. An IS-VLC system is designed and the experiment is conducted to evaluate the performance. Compared with the Hough transform based LED array detection, it is proved that the proposed algorithm has lower bit error rate (BER) and shorter operating time.