Begin with the story's sources of tension
The dream adventure includes snakes, wolves, pursuit, threats, parent-child separation and sacrifice. The imagery is not realistic horror, but children sensitive to animal attacks, separation or injured characters may still find it stressful.
Growing up, courage and responsibility are central themes. Parents can explain beforehand that the story passes through fear and loss in order to ask how someone can still choose and act while afraid.
Then consider the viewing experience
The film runs about 86 minutes. Rough 3D imagery, sudden sound and laughter from a cinema audience can all affect a child's experience. Meme-driven group reactions may also make the emotional tone harder to read.
A mainland China public-screening licence is not an age-specific parental rating. This site therefore does not prescribe one universal age: for young or sensitive children, review the plot first, watch together and keep the option to leave.