Mount Merapi, one of the active volcanoes in Indonesia, has been recorded to have experienced 84 eruptions until 2010. Debris flows can occur due to the intensity and duration of rain simultaneously, which causes the debris flow process to occur. Therefore, this is the basis for conducting research on rain on the occurrence of debris flows in the Putih River that occurred after the 2010 eruption of Merapi using the critical line method. The secondary data used in this study are rainfall data obtained from the Agromulyo and Ngepos rainfall posts as well as lava flood incidence data recorded at the Mranggen dam check. Based on this data, data will be obtai ned in the form of cumulative rainfall, rainfall intensity, working rainfall, and critical line. Based on the results of the analysis that has been carried out, it was found that the cumulative rainfall that affects the debris flows in the Putih River averaged 0–20 mm. The most frequent occurrences of debris flows occurred at the intensity of 0–10 mm/h with 19 occurrences and the intensity of 10–20 mm/h with 16 occurrences at 2 rain stations. In this study, the average danger level is at levels 1 and 2, which are alert levels, but some incidents that occur are at level 3, and there are even incidents above level 3.