The carbon trading pilot scheme will provide additional financial support for investment in afforestation carbon sequestration projects. However, the successful implementation of afforestation carbon sequestration projects under this mechanism still faces great uncertainty of economic policies. Considering these characteristics, revealing the critical threshold of investment timing and the option value from the perspective of investors can provide a more comprehensive reference for the optimal decision making of investors and policy making for the government to promote investment in afforestation carbon sequestration projects. Therefore, based on the theory of optimal investment timing of real options, the value of carbon sequestration afforestation project is measured by the Faustmann-Hartman model, and the analytical expression of optimal investment timing and option value of carbon sequestration projects in the early planning stage and project construction stage is solved by the dynamic programming method. Then, the critical threshold of optimal investment timing and the investment options value of Pinus elliottii afforestation project are empirically examined and simulated. The results show that: (1) The investment options value of Pinus elliottii afforestation carbon sequestration project is 0.12 yuan/hm² in the project planning and filing stage and 0.59 yuan/hm² in the project construction stage, respectively. The critical threshold of optimal investment timing is 79.23 yuan/t and 57.33 yuan/t, respectively. Rational investors will only invest immediately when the carbon price are above the critical threshold, otherwise they will choose to delay their investment. (2) Carbon price volatility, carbon sequestration transaction cost, and labor price variables have significant positive effects on the critical threshold of optimal investment timing and investment option value of Pinus elliottii afforestation project for carbon sequestration. With the increase of value of the above variables, the investment options value and the critical threshold of optimal investment timing will also increase, but it will delay the timing of investment. (3) The increase of timber price and the success rate of project filing will decrease the critical threshold of optimal investment timing. That is, the increase of value of the above variables can shorten the time for investors to delay investment. The study concludes that in order to promote investment of afforestation carbon sequestration project and for forestry to play the role in coping with and adapting to climate change, relevant government authorities need to establish and improve carbon price fluctuation control policies and project record management policies. At the same time, comprehensive measures should be taken to reduce carbon sequestration transaction costs. In addition, considering the long-term and public welfare characteristics of forestry investment and the rising trend of labor factor prices in China, it is necessary to establish and implement forestry carbon sequestration subsidy system in the future.