This paper analyses the effects of resin benefit on the optimal rotation age of Simao pine plantation. Timber growth and resin yield functions were first derived, and then an integrated formulation for Hartman rotation was solved by taking both timber and resin benefits into consideration through numerical optimization. Empirical results indicate that: (1) the inclusion of resin benefit results in lengthening optimal rotation age; (2) resin benefit has a greater effect on rotation age when discount rate is low than when it is high, ceteris paribus; (3) with an improvement of site productivity, resin benefit has a decreasing effect on rotation age, other factors being constant. These effects are also true with respect to benefit gains in present value.