Based on conventional observations，radiosonde data，ERA5 analysis data，and data of regional automatic meteorological station and Doppler radar，this paper analyzes the environmental background and radar echo of an EF2 tornado triggered by Typhoon Yagi in the North Shandong Plain on 14 August 2018． The results are as follows． (1)When the tornado occurs，Typhoon Yagi has weakened to an extratropical cyclone and its numbering has been stopped． (2)Favorable environmental conditions for the tornado include low-level convergence and upper-level divergence，good overlap of upper and lower jets，strong low-level vertical wind shear，storm-relative helicity (SRH)and so on． (3)The tornado- parent storm is a mini-supercell storm，and the low-level reflectivity still has a hook echo；on the velocity profile，it has the characteristics of axis of tornado vortex and convergence of the small-scale wind field，and the corresponding spectral width profile has a high-value area． (4)After lowering the thresholds of some adaptation parameters of the mesocyclone detection algorithm and tornado vortex detection algorithm in the radar system，the system gives the mesocyclone features 60 min in advance and tornado vortex signature (TVS)7 min in advance． The rapid rise and fall of the top height and maximum shear height of the mesocyclone correspond to the enhancement and touchdown of the small-scale vortex，and the sudden drop of the maximum shear value corresponds to the rapid release of energy from the tornado．