Transportation sector is both a fast-growing energy consumption department and an CO_2 emissions department. Its CO_2 emissions peaking time and level has been a key factor affecting Chinese achievement of National Determined Contributions around 2030. The dynamic Kaya analysis of CO_2 emissions in transportation sector has been applied,and has deduced the necessary conditions for CO_2 emissions,energy consumption and transportation volume to peak,as well as the general rule of the time order of these peaking. The result shows that CO_2 emissions peaks firstly appear when the annual decrease rate of CO_2 emissions per energy consumption surpasses the annual increase rate of energy consumption. Energy consumption peaks secondly appear when the annual decrease rate of energy intensity of transport volume exceeds the annual increase rate of transport volume. Transport volume peak appears at last when the annual decrease rate of transport volume per GDP overtakes the annual increase rate of GDP,which also means the development of transportation sector is decoupled from GDP growth. Considering the new normal of Chinese economy,scenario analysis is adopted to estimate the peaking of CO_2 emissions,energy consumption and transport volume. The result shows that only by adopting collaborative measures including fiscal policies of fuel oil tax and carbon tax as well as fuel replacement and transport energy efficiency promotion,CO_2 emissions peak in transportation sector will be realized around 2035 with about 1.23 billion tons of CO_2 emission,and energy consumption peak can be realized around 2045 with the amount of 740 million tons of coal equivalent. Though transportation volume peak may not be achieved before 2050,the increase rate could be quite slow. Compared with the development of transportation sector in the USA,Japan and EU when their CO_2 emissions reach the peak,China's transportation sector has an obvious features that fast development accompanies with green and low-carbon transition,and the above three peaks appear step by step observably. Therefore,the top-level design in China's transportation sector should be fully strengthened,and the comprehensive transport policies system should be established. Taking low-carbon transport technologies as an important starting point,the peaking of CO_2 emissions in China's transportation sector can be accelerated through making full use of market mechanism of emission reduction and fully enhancing the public awareness of low carbon travel.