Abstract: The finite element and boundary integral equation method (FE-BI) is adopted to analyze the influence of structure parameters on conical log-spiral (CLS) antennas in the paper. Firstly the radiation performance of conical spiral antennas at different frequencies are analyzed. Then the influence of pitch angle and cone angle are discussed respectively. Numerical results show that radiation properties of conical log-spiral antennas are greatly changed by these parameters, which should be fully considered in practice.