Abstract: The project of mining investment could be regarded as a relayed call option. Aiming at the defects of the traditional discounted cash flow (DCF) method，a trinomial tree pricing model of the real option is improved in the case of Molybdenum ore. A theoretical method for the hurdle price under the best investment timing is constructed. The real data is used to simulate the option pricing，and the result show that this method is reliable and practical. Meanwhile，according to the characteristics of the metal mine，the influence of price fluctuation on the cut-off grade，reserve estimation，mine service life is quantified to enhance the accuracy for mining investment by the option theory.

Key words: Real option approach(ROA), Trinomial tree model, Hurdle price, Cut-off grade