A number of different lahars were recognized during the systematic survey of a mapping project. The high setting temperature feature of the deposits indicates a relationship between the lahar and the Millennium eruption event of Tianchi volcano. The lahars caused serious disasters. Recognition of the huge avalanche scars and deposits around Tianchi volcano implies another highly destructive hazard. Three different structural types of the avalanche deposits have been recognized. There frequently existed magmatic mixing processes during the Millennium eruption of Tianchi volcano, indicating a mixing and co-eruption regime of the eruption. This paper has also discussed some features of the historically accounted eruptions.