This article gives a brief account of Academician Qian Xuesen´s life and reviews his outstanding contributions to the development of China´s science and technology in over half of the past century. He always takes Marxist philosophy of dialectical materialism as foothold and starting point whenever studing and obseving problems. He stated that all the modern scientific and technological disciplines should belong to the knowledge hierarchy which was under the guidance of Marxist philosophy of dialectical materialism. The article describes that 50 year ago Qian had made a penetrating exposition on the dialectical relationship between science and technology. His scientific thesis still has important directive function in formulating and promulgating China´s scientific and technological policies. The article devotes a lot of space to describing Qiao´s contributions to engineering cybernetics and systems science. The article also describes the worldwide repercussions and influence evoked by the publishment of Qian´s book Engineering Cybernetics. Besides,Qian summed up the conept and method of systems engineering based on his working environment and experience. This concept has been accepted by many statesmen for analyzing and solving key issues.