The invention discloses a density detection system comprising a robot for clamping a to-be-detected pipe with to-be-detected particles loaded and driving the to-be-detected pipe to move to a preset position, a pipetting device, an image acquisition device, and a computing device. The pipetting device includes a driving assembly and a pipetting pump connected with the driving assembly; the pipetting pump is used for sucking a basic titration solution; and the driving assembly is used for driving the pipetting pump to move above the to-be-detected pipe to dropwise add the basic titration solution. The image acquisition device includes a camera and is used for collecting an image of the to-be-detected tube after the basic titrating solution is dropwise added. The computing device connected with the camera is used for acquiring the image collected by the camera, determining whether the to-be-detected pipe reaches a titration end point or not according to the image, indicating the pipettingdevice to dropwise add a titration solution with the density different from that of the basic titration solution into the to-be-detected pipe after determining that the to-be-detected pipe does not reach the titration end point, and using the density of the liquid in the to-be-detected pipe as the density of the to-be-detected particles after determining that the to-detected pipe reaches the titration end point. In addition, the invention also discloses a density detection method.