The invention discloses a passive optical network performance data collecting device and a passive optical network performance data processing method. The method comprises that, firstly, a timer units periodically transmits timing messages to a performance module; secondly, the performance module decides whether data passes through a performance dump unit to a data collecting unit according to that the current moment is a performance dumping moment; thirdly, the real-time rate of the performance data is obtained through a performance data processing unit; finally, by comparing the real-time rate of the performance data with a threshold value, whether to issue alarm can be determined. According to the passive optical network performance data collecting and the passive optical network performance data processing method, data collection and processing operations can be completed in the background; the passive optical network performance data collecting device obtains good expansibility and can expand the performance data without adding new tasks; the passive optical network performance data processing method can obtain the real-time performance and the historic performance of a device at any time after a performance collecting task is started.