The method of calculating interchange noise was studied according to geometric alignment.By using vehicle speed as starting point,the relationship was fitted between noise levels and vehicle speed.For the calculation of ramp noise,the thesis defined the concepts and calculation method of relative equivalent sound energy according to the definition of equivalent sound level,determined the total noise energy by using the method of adding noise energy in uniform motion segment to the one in variable motion segment,and established the functional relationship between relative equivalent energy and the length of ramps.Under the definition of equivalent sound level,the noise level of left-turn ramp and right-turn ramp were deduced by the method of ramp length integral operation.For the calculation of the main line noise,the formula of the main line noise level was deduced according to the relationship among the mainline design speed,noise level and vehicle speed.The total interchange noise was obtained by the superposition of noise level in each main line and ramp.Heda interchange in Heilongjiang province was taken for example.The result shows that this method can solve the calculation problem of noise pollution in interchange ramp variable motion segment,and can connect the noise pollution produced by traveling vehicles with the interchange geometric alignment.When the interchange geometric alignment design conditions are known,the noise pollution can be calculated and the results can be used to quantitatively evaluate the degree of interchange noise pollution.