Because Sima Guang was Wang Anshi's good friend when Wang Anshi's political reform was implemented, but he did not support the political reform. Therefore, after the success of the political reform, Sima Guang became an obstacle to the political reform in the eyes of the new official, and then proposed to open the coffin, but in the end it was not implemented. In the middle and late Northern Song Dynasty, the national strength declined, and Wang Anshi thought of reforming to save the Northern Song Dynasty. However, in the process of political reform, because it touched the interests of conservatives, the new school headed by Wang Anshi had strong differences with conservatives. The imperial court was also divided into two factions, which led to a partisan struggle.

After Wang Anshi put forward the political reform, Sima Guang resigned and retired directly, and started his book-editing career. Later, Sima Guang returned to the imperial court again, and when Wang Anshi's political reform touched the interests of the people, Sima Guang began to oppose it, so the conservatives directly classified Sima Guang as a conservative, and the new school also thought that Sima Guang's opposition to political reform was against the new school.

It's just that Sima Guang didn't take sides himself. It was only because the reform touched the interests of the people that Sima Guang opposed the reform for the people. However, he still supported some measures in the political reform, because his political views were different from Wang Anshi's and his attitude towards the political reform was different, and his former friends could only go their separate ways.

Both Sima Guang and Wang Anshi had good intentions, both for the development of the Northern Song Dynasty, but Sima Guang had no doubt about Wang Anshi's character. Just because of Sima Guang's stubbornness, he became the object of new hatred. Sima Guang had been working before his death, and Wang Anshi died five months earlier than Sima Guang. After Sima Guang's death, everyone came to pay their respects, but his room was very poor, and there were only some books on the shelves. After the death of Sima Guang and Wang Anshi, the struggle between the old and new parties has not stopped, but has intensified. The new faction came to power, thinking that Sima Guang was the leader of the conservatives and wanted to open the coffin for autopsy. Fortunately, this opinion was not adopted.