It is the core and bottleneck of equipment fault diagnosis technology by using the online oil monitoring to characterize the abnormal wear state information of machines.Aimed at the existing problems that the offline lubricating oil monitoring method is unable to reflect promptly the lubrication oil condition in an offshore drilling platform,the online oil monitoring was carried out on 5 engines of the offshore drilling platform.The constitution of online monitoring system platform and implement plan were introduced.Aimed at the fault alarm that the amount of large grains exceeds the standard by realtime monitoring in the oil,through the offline ferrography analysis,the accuracy of monitoring results is verified.