The invention discloses a method for quantitatively analyzing an influence exerted by bilateral trade on a power grid power transmission cost. The method comprises the following steps: step 1, determining a calculation period of a power grid power transmission cost analysis, and generating a typical daily load curve; step 2, based on the typical daily load curve, without considering system bilateral trade, establishing an optimization analysis model of the power grid power transmission cost, and calculating a reference state of the power grid power transmission cost analysis; step 3, calculating a marginal obstruction cost and a marginal network loss cost of each node in a power grid in each time period, and obtaining a marginal power transmission cost of each node; step 4, calculating a typical daily generating amount of a set participating in the bilateral trade, expanding the typical daily generating amount in a bilateral trade period, and obtaining a set reference electric quantity of the power grid power transmission cost analysis; and step 5, comparing a bilateral trade electric quantity with the set reference electric quantity, and through combination with the marginal power transmission costs, calculating the influence exerted by the bilateral trade on the power grid power transmission cost. According to the invention, quantitative analysis of the influence exerted by different bilateral trade on the power grid power transmission cost can be facilitated.