High mountains and canyons in Northwest Sichuan are developed, and earthquakes are frequent. Lengzhuguan area belongs to granite high and steep slopes. Such high and steep slopes in canyons in Western China are representative. It is of great significance to study the response law of seismic waves under this specific geological condition. The Hanyuan Ms4.8 earthquake triggered four strong earthquake recorders arranged on the lengzhuguangou monitoring profile in Luding County. By analyzing the monitoring data recorded this time and comparing with the previous research results, it is revealed that: (1) The amplification effect of granite on seismic waves is stronger than that of mudstone. The intensity of granite slope is greater when the seismic waves pass by, and it is more prone to instability failure; (2) The predominant frequency of strong earthquakes on the right bank of Lengzhuguan is 2~6Hz, and the predominant frequency on the left bank is 7~13Hz. The predominant frequency of seismic waves on granite high and steep slopes is mainly ultra-low frequency in the peninsula shaped ridge, and the median low frequency in the thick mountain slope. In the possible earthquakes in the future, the slope and seismic waves with predominant frequencies within this range are more likely to resonate, resulting in strong seismic response of the slope; (3) The amplification effect of granite slope on seismic wave in the same slope direction increases with the increase of earthquake magnitude. The back slope effect caused by different incident directions of seismic wave has more obvious influence on the amplification effect of slope than that of earthquake magnitude.