In this talk, I will introduce my recent work on computing the transition pathways in Cylinder-Gyroid interface. As a preparation, I will first introduce the background of modulated phases, including some models and computational methods. Then I will focus on the Cylinder-Gyroid interface system. We propose a projected index-1 saddle dynamics method to find the transition state with mass conservation. Furtherly, four basic transition pathways connecting different local minima will be depicted in detail, which represent four different mechanisms.