Although lung cancer screening with low-dose CT (LDCT) can reduce lung cancer mortality by 20%, without an appropriate eligibility criteria, it may result in a waste of medical resources and a degree of unnecessary damage to participants' health. This study aims to give the optimal screening strategy in China based on cost-effectiveness analysis on pros and cons of different situations. From the perspective of primary healthcare system, a Markov model was built to simulate LDCT screening of 100,000 heavy smokers (>30 pack years) aged 40 in different situations. Model parameters mainly came from screening programs conducted in China and other countries, official public data, and published literature. Two indicators of primary outcome, incremental cost-effectiveness ratio (ICER) and net health benefits (NHB), were compared with those of no screening. Sensitivity analysis was conducted to evaluate model uncertainties. We defined the optimal strategy as the one with both acceptable cost effectiveness and maximal NHB. Base-case analysis results showed that for all screening strategies, ICERs were less than three times of GDP per capita. As for NHB results, it showed that when the willingness to pay for screening was less than three times of GPD per capita, the largest NHB was obtained in the strategy which started screening at 50 years old and this strategy showed stable performance in univariate and probabilistic sensitivity as well.