The invention provides an ultraviolet fluid treatment device, and concretely relates to a medium-pressure and/or low-pressure mixed novel ultraviolet fluid treatment device. Medium-pressure and/or low-pressure ultraviolet lamp tubes in the device refer to a medium-pressure multispectral ultraviolet lamp tube, a low-pressure ultraviolet lamp tube or an excimer ultraviolet lamp tube which are mounted in a mixed manner (the device comprises ultraviolet lamp tubes with two or more different types and/or powers). An ultraviolet intensity sensor assembly monitors the luminous intensity of the ultraviolet lamp tubes in real time and feedbacks the monitoring result to a control system, and the control system can automatically adjust the powers of the ultraviolet lamp tubes according to a feedbacksignal, and can give an alarm for reminding when the intensity is insufficient and automatically adjust the powers or close the specific lamp tube during insufficient flow or special application in order to adaptively adjust the power of the system, so that the working efficiency is greatly improved.