Applying real option theory and method, we establish a firm's pollution abatement investment decision-making model with the uncertainty of emission permits trading price. We show that, when emission permits are allowed or not allowed to inter-temporal trade, compared with the results of applying net present value method, the uncertainty of tradable emission permits price makes firm delaying pollution abatement investment. Under emission permits inter-temporal trade, the uncertainty of tradable emission permits price does not incentivize firm investment ahead of time, and when the marginal valu...