Abstract: The Arxan volcanic group is one of the most important volcanic groups in the Quaternary in Northeast China. It is of great significance to obtain information of crustal structure and v_P/v_S ratios in this area for studying the physical properties of the crust and tectonic evolution beneath the volcanoes. Original waveform data came from temporary broadband seismic stations in the Arxan volcanic area. The crustal thickness and average v_P/v_S in the study area are obtained by the P-wave receiver function and H-κ stacking method. The results show that the crust thickness is thicker in the northwest and thinner in the southeast, ranging from 33.9 km to 37.9 km, with thinner crust near the volcanic belt. There is a positive correlation between crustal thickness and elevation. The v_P/v_S ratio ranges from 1.73 to 1.83. There are three high v_P/v_S ratio areas in the study area: Chaihe town-Mingshuihe town, the north of Yimin Doren and Tianchi town. The thin crust and high wave velocity ratio areas beneath Arxan volcanic region may be caused by the upwelling of mantle material and underplating of basaltic magma.