Based on FY 2E meteorological satellite images and CINRAD data, this paper analyzes the trigger conditions to the tornado weather seen on 15 May 2010 in the west of Heilongjiang Province. By analyzing the circulation and mesoscale characteristics from satellite images, this article reveals the formation conditions of thunderstorm clouds that generate and trigger the tornado. The characteristics of cloud images and radar echoes of the tornado event is illustrated in detail on the basis of CINRAD data. The main results are as follows: The mesoscale convection process occurs in front of the upper trough and surface cold front, and the α mesoscale convective clouds are developed by multiple small scale convections. Unstable energy of tornado is provided by humidity gradient, water vapor transportion, vertical wind shear and dry intrusion, and the surface cold front provides the trigger mechanism. The thunderstorm clouds constantly generate and dissipate combining with other thunderstorm clouds during the developing process. The tornado is produced when two clouds amalgamate. The characteristics of the radar echoes are very obvious. At the mature stage of the storm, the hook echo and bounded weak echo regions become the largest, the downdraft begins to interact with the inflow producing the outflow boundary and there is a clear gale area in the high, middle and low levels. The tornado occurs in the vicinity of the echo.