1. Geology Date Museum of Jilin Province，Changchun 130061，China; 2. Institute of Geologic Survey of Jilin Province，Changchun 130061，China; 3. Jilin Geological Exploration Institute，China Chemical Geology and Mine Bureau，Changchun 130061，China; 4. College of Earth Sciences，Jilin University，Changchun 130061，China

The whole rock K- Ar dating method was used to date the basalts from Laodaoshan-Shuangshan- Maoshan- Sijiashan volcanic cones in Jian'an volcano group of Liaoyuan，which are (99. 28 ±1. 59) Ma，(91. 70 ± 1. 67) Ma，(82. 55 ± 1. 94) Ma and (82. 18 ± 2. 37) Ma，respectively． The results show that Jian'an volcano group was the largest Late Cretaceous volcano group in Northeast China or even in East China． This investigation provided exact chronological data for Late Cretaceous tectonic evolution in East China． The formation of this volcano group had close relationship with the inorganic origin reservoir，and also provided basis for prospecting of sapphire or its associated deposits．