There are many reasons why kids with autism get upset easily.
They experience the world differently and can get overwhelmed. Some things that we barely notice can be very stressful to them. For example, sensory stimuli like lights, sounds, smells or textures.
Many kids with autism have trouble communicating their needs. This makes everything more stressful. Imagine if you had to walk around all day with a stone in your shoe and a loud buzzing in your ear, but you could not tell anyone what was annoying you.
Here's what you can do:
Understand your child's triggers. (These are the things that make them upset.)
Minimize these triggers if possible at home, school, and wherever they spend time.
Create a strategy to warn and prepare them if they are going to be in a stressful situation.
Have a place they can go to calm down, or a process that they can use. This may be going to a quiet corner of the room, putting on headphones and listening to music, sitting in your lap, or taking a lap around the room or block.
Use visual supports to help them know what to expect.
Work on ways to help them communicate their feelings and needs. Speech therapists can help with this.
Read this Bog Post, written by an autistic adult who advises parents: Anxiety Looks like Anger.