The reason why Shen Shixi's animal novels were so sad was that they expressed the author's thoughts and feelings about life and fate through describing the encounters and fates of animals. Shen Shixi's animal novels usually depicted the living conditions of animals in the natural environment, such as being attacked by predators, being harmed by humans, losing their homes and partners, and so on. These encounters not only made the animals feel lonely and helpless, but also reflected the author's cherish of life and love for nature. Shen Shixi's animal novels also expressed his thoughts on human behavior. In the works, animals were often subjected to cruel treatment by humans, such as locking them in cages, slaughtering them, destroying their habitat, and so on. These actions not only violated the basic rights of animals, but also violated human values and moral standards. Therefore, Shen Shixi's animal novels called for people to respect the lives and rights of animals and protect the natural environment and animal habitat. Shen Shixi's animal novels also used delicate descriptions and vivid language to make readers deeply feel the emotions and fates of animals. These descriptions not only showed the pain and struggle of the animals, but also expressed the author's thoughts and feelings about life and fate. To sum up, the reason why Shen Shixi's animal novels are so sad is that they express the author's thoughts and feelings about life and destiny through describing the encounters and fates of animals. At the same time, they also call on people to respect the lives and rights of animals and protect the natural environment and animal habitat.