The M_L3.8 earthquake that occurred on October 1, 2013, in Rushan at 12:07 is located in Shandong Province's northeast section. Then the earthquake swarm activity was formed. A total of 13 000 seismic records were obtained in the seismic network at Shandong so far. The largest earthquake on May 22, 2015, is M4.6. During 2011-2014 we collected the teleseismic waveform from Rushan station to calculate the receiver functions, then we calculated the crustal thickness and velocity ratio in the focal region and its adjacent regions. The results showed that the lateral heterogeneity of the crustal velocity structure in the study area is high, and the receptor functions observed differently in different azimuth. There is an obvious difference between the source area and the adjacent area. In the middle and lower crust of source area, there is an obvious low-velocity zone but high-velocity zone in the middle and lower crust of its neighboring areas. We used the receiver functions stacking method H-k to determine the crustal thickness and wave velocity ratio of the seismic source area and adjacent area. The results showed that the thickness of the crust is 31 km, and the wave velocity ratio is 1.74. Many earthquakes above M_L3.0 occurred in the high and low-velocity junction regions. It was inferred that the occurrence of the Rushan earthquake swarm may be due to the upper crust rupture caused by the heterogeneity of matter within a small scope.