This paper establishes a new transmission network planning model considering uncertain information. The proposed new model is based on the traditional model under certain information， and some new constraints are added to remain reserved transfer capability and adapt to the changing of uncertain loads. In the new model， the constraint of loading rate of transmission line is included to satisfy the long-term， small uncertain load fluctuation; the constraint of regional load increment is included to satisfy the uncertain locations of short-term， and large load increments. An improved greedy randomized adaptive search algorithm is applied to solve the proposed new model. In the new model， the uncertain loads need not model in detail. The proposed new model is easy to solve and has better adaptability. The numerical results on the 46-bus testing system validate the correctness and effectiveness of the proposed new model and algorithm.