Aiming at multi-attribute decision(MADM) problem in transmission network planning, an interval analytic hierarchy process(IAHP)-based method of transmission network planning is proposed. The method improves traditional analytic hierarchy process by using interval data instead of dot data, dispose rationally uncertainty of decision factor and fuzz of judge of experts and boosts up reliability of evaluation result in transmission network planning. The method adopts upper model and lower model method to resolve weight. The idea is changing weighted resolve of judgment matrix to linear programming problem by referring upper approach Concrete algorithm and improves efficiency and precision of calculation. Case results show that the method has fast speed and, high accuracy.