He was one of the three leaders of the Nepali Congress in the late 1940s, opposing his relatives, the Rana family, who held power in Nepal at the time.

Subarna Shamsher played a crucial role during the movement to attain democracy in Nepal and to remove the Rana rule.

In 1950, both Bishweshwar Prasad Koirala and Subarna Shamsher realized that the only way that the movement would succeed would be through the merger of their respective political parties.

After a string of talks and negotiations Subarna Shamsher made Koirala realize that violence will be needed and thus, the two parties came together to form the Nepali Congress.

After the merger he spearheaded the movement and enabled it to arm and train a small army which then began destabilizing the Rana government in eastern parts of Nepal.

With situation getting worse for the Rana governor, the Royal Army eventually retreated from most of eastern Nepal which then came on the control of the Nepali Congress.

In 1951, he became the Minister of Finance in the interim Congress-Rana government led by Sir Mohan Shamsher Jang Bahadur Rana.

All his property in Kathmandu was seized by the government which included the Lalita Niwas estate which was later on turned into the headquarters of the Nepal Rastra Bank.