I want to control 3.5new particlesystem by C#，the radius of shape ，but i cannot find the API ，so i want to find the way of control the shape radius of new particlesystem，thanks！！！
Here you go Unity - Scripting API: ParticleSystem.Emit
Also, when you put in a component in Unity, there is a book which is a reference page. Just search through each of the functions to find what you are looking for. I found it in 3 mins.
Here’s how you can do it. Create a new animation clip. Then add an animation component to your particle system. Assign the new clip to it. Next open the animation editor and adjust the radius values for the particle system and set the desired key frames. Finally write a script to play the animation.
Hope that helps.