A droplets detecting system (100) includes a laser diode assembly (20), a photo diode (30), a light source (40), a charge coupled device camera (50), a signal processing and displaying device (32), and an image processing and displaying device (52). The laser diode assembly is configured for emitting a laser light (26) to pass through a droplet (204). The photo diode is configured for receiving the laser light passing through the droplet and for generating an electronic signal. The light source is configured for emitting an illuminating light (42) to illuminate the droplet. The charge coupled device camera is configured for receiving the illuminating light and photographing the illuminated droplet. The signal processing and displaying device is connected with the photo diode and is configured for displaying the electronic signal generated by the photo diode. The image processing and displaying device is connected with the charge coupled device camera.