Sikap, a little boy, was born in Weijing, and Weijing killed dragons for generations. By chance, Hikarp met a fierce dragon night demon. Hikarp didn't hurt it, but became good friends with it and named it "Toothless". In the days of getting along with toothless, Hikarp learned a lot about the weaknesses of dragons and found that they were not terrible. Later, the girl astrid discovered the secret, and they understood that the dragon didn't want to hurt human beings. They took the cattle, sheep and livestock, because there was a big dragon waiting in the cave. If they don't bring enough food, they will be killed ... Finally, Sikap killed the dragon with toothless drive, and the Weijing people and the dragon became good friends.
In the movie, many dragons attacked the vikings living on the island. However, the little hiccup, the son of their leader, was very weak. People thought he couldn't compete with the dragon, so they let him stay at home. However, Hiccup refused to admit defeat. He rushed out alone and ran into the shadowy dragon "Night Devil". One day, he went to the place where the nightmare fell and found the nightmare lying there. He was afraid and wanted to kill it and kill the people, but later he couldn't bear to do so. From then on, he sent food to the nightmare every day and gradually tamed it. Later, the Vikings began to train children in dragon training. Hiccups make rapid progress and perform well. A little girl named Ai Strede was surprised. One day, she followed Hiccup to find the nightmare. Hiccup told her not to be afraid and kept her secret. Later, the nightmare took them to the dragon's habitat. They realized that every dragon had to give the dragon food, so they robbed the Vikings. If you don't give it, you will be eaten. When training a dragon, Hiccup was in danger again. The nightmare came to save him, but the vikings caught him. Let nightmares guide them to the dragon's habitat. However, after a life-and-death struggle with the dragon, the nightmare gave his life to save the little brother, and people lived in harmony with the dragon from then on.