As the direct subject of collective forestland tenure reform, increasing farmers’ income is an important goal of collective forestland tenure reform and the key to sustainable management of forest resources. Based on the survey data of 1276 rural households in 18 counties in 9 provinces, we construct a theoretical analysis framework of the impact of collective forestland tenure reform on household income from the perspective of rural household differentiation and elucidate the mechanism of the effect of collective forestland tenure reform on household income in the context of the rural household differentiation. The results of the empirical analysis show that, firstly, the collective forestland tenure reform significantly increases the total income, forestry income, and off-farm income of rural households, but the effect of income increase differs significantly among different groups of rural households with different income levels, showing the characteristic of “benefitting the rich more than the poor”. Secondly, as rural household differentiation deepens, there is a moderating effect of rural household differentiation in the income-raising effect of collective forestland tenure reform, i.e., collective forestland tenure reform has a stronger marginal effect on the forestry income of shallowly differentiated rural households and a weaker marginal effect on their off-farm income compared to deeply differentiated rural households. Finally, the income increase effect of collective forestland tenure reform shows significant situational dependence in both forestland operation scale and human capital endowment. The income-raising effect of collective forestland tenure reform is stronger for forestry income of large operation scale farmers, while it is stronger for off-farm income of small operation scale farmers; the income-raising effect of collective forestland tenure reform is stronger for farmers with high quantity and quality human capital endowment than for farmers with low quantity and quality human capital endowment. Therefore, this paper attempts to provide a policy adjustment idea to deepen the policies related to collective forestland tenure reform by starting from the farmer differentiation side.