Abstract： In-situ collapse blasting demolition technology is a new blasting demolition technology which can break through the condition of serious shortage of collapse space for towering chimneys． The difficulty of this technology is to set up efficient operation platforms at multiple locations at hundreds of meters to quickly complete drilling， charging，stemming and networking，thus forming multiple ring blasting cuts． According to the requirements，a variable diameter hanging basket as a construction platform is developed． The overall design idea of the new operation platform is as follows: The core function of the platform is defined based on the analysis of the operation process，and the variable section basket platform with a sliding plate is selected by comprehensively considering various factors such as efficiency，reliability，adaptability and cost． A parametric model is established to determine the optimal values of the length and included angle of the fixed section and the sliding plate of the hanging basket for different chimney dimensions，which is according to the adaptability of the platform to the overall dimension of the chimney． The technical schemes of the telescopic structure are compared and selected，and finally the steel wire rope traction scheme together with the resistance reduction scheme by tetrafluoroethylene plate is selected． On the basis of the above technical scheme，the structural scheme，safety guarantee scheme，adaptive design scheme，installation，disassembly and using scheme of the platform are determined． In order to verify the reliability of the structural design，the stress analysis of the structure under various working conditions is carried out by using the finite element software． Meanwhile，a special test frame is set up，and a series of tests including functional test，load test and reliability test are carried out on the first test prototype to verify the safety and functional reliability of the platform structure． The test results show that all the functions of the platform reach the design expectations，and the structural safety and functional reliability meet the requirements． The platform can meet the needs of in-situ collapse of towering chimneys by blasting demolition， and can also be used as a construction platform for the demolition of other high-rise structures with variable crosssections．