Ocean-effect events take place frequently in winter in the Bohai Sea region. Based on the satellite data of GMS5, GOES9 and MTSAT, NCEP FNL reanalysis data, SST, and observed surface precipitation data from 2000 to 2012, the seasonal and diurnal variation characteristics of the ocean-effect events in the Bohai Sea are systematically studied. The results are listed as below. 1) The ocean-effect events in the Bohai Sea generally do not last for a long time. The cases of long duration happen from November to next January, and this period sees the most events. 2) The occurrence of ocean-effect events has obvious diurnal variation characteristics. The probability of occurrence in the morning is obviously greater than that in the afternoon and the early night, and the probability is not the same in different seasons. 3) About half of the ocean-effect events cause precipitation in the Shandong Peninsula, mainly snow in winter and rainfall in some cases. 4) In addition, the environmental indicators causing ocean-effect events also have strong monthly variation characteristics. The monthly variations of temperature at 850 hPa, sea surface temperature, temperature at 2 m, and specific humidity are obvious, while the wind speed and the temperature difference between sea surface and 850 hPa are relatively constant and have little seasonal change. These results will further deepen the understanding of ocean-effect events in the Bohai Sea and provide reference for forecasting and profound research.