Abstract:Major achievements of space science and technology are important symbols of a country's scientific and technological level and ability. The basic consensus of the aerospace community is that China's space technology has been well-developed, space applications need to be strengthened, and space science is relatively the less-developed. Thus, it is extremely urgent for China to build a strong country in space science and tackle the "bottleneck". Here we elaborate the internal logic among the strength of S&T, aerospace, and space science, expound the connotation of space science strength, investigate the index system, and suggest the three-tier system scientifically for the first time. On this basis, this study analyzes China's world position, finds the main gap, and puts forward several suggestions for its future development. Although this outcome indicates that China is in the third place in global space science, it should not be over interpreted. On the contrary, the core aim lies in that we should accelerate the development of space science with 15% growth of the national space science investment in the limited time window period of the next 15~30 years, and build up the leading space science and accomplish major original breakthroughs, the primary sign of China as an aerospace strength and S&T strength in the middle of 21st century.