Impact & fracture toughness properties of steel plate and welding joint of WEL-TEN610CF for natural gas spherical tank were investigated.The WEL-TEN610CF steel plate as tempering and tempering+SR treated show good impact property at -20 ℃.Steel plate and welding joint of WEL-TEN610CF show good fracture toughness at -20 ℃.It is feasible to use WEL-TEN610CF to manufacture oversize natural gas spherical tank which is used over -20 ℃ operating condition.Welding material used in the test is a match for steel plate,the welding process is appropriate.