The invention discloses a detection device for detecting petroleum density, belonging to the technical field of petroleum detection, and comprises a mounting plate, a conveying assembly, a moving assembly and a cleaning assembly, wherein the top part of the mounting plate is provided with a petroleum density detector, the conveying assembly comprises a conveying member, a rotating member and a clamping member, the conveying member is arranged at the top part of the mounting plate, the rotating member is arranged on the conveying member, the clamping member is arranged on the rotating member, the moving assembly comprises a moving member and a limiting member, the moving member is arranged at the top part of the mounting plate, the limiting member is arranged on the moving member, and the cleaning assembly is arranged on one side end portion of the conveying member. According to the detection device, the positioning plate is driven to move on the positioning block by means of a mobile cylinder, so as to move a cleaning roller into a petroleum detecting vessel in the limiting groove; and the cleaning motor operates to drive the cleaning roller to rotate for performing cleaning operation on the petroleum detecting vessel, the cleaning operation of the petroleum storage device is realized, thereby facilitating the detection of petroleum next time.