From the 1950s to the 1970s，Sri Lanka was a global model of development among third world countries. Through its active participation in the Non-Aligned Movement，the country raised its voice in the global political arena and，by inheriting its ‘colonial legacy’，was ahead of most developing countries in terms of infrastructure，economic base and social welfare. After years of civil war，Sri Lanka was also reborn with great potential for development，but in 2021 it fell into the most severe economic crisis since independence. In terms of economic logic，the chronic twin deficits and high reliance on external debt to maintain a balanced development model are the root causes of Sri Lanka’s economic development vulnerability and cumulative debt risk，while external shocks such as the spread of the new crown epidemic，the outbreak of the Ukraine crisis and the breakdown of global supply chains are the real causes of interrupting the country’s fragile economic development and external debt sustainability balance；behind the economic logic，there are institutional，historical，social and external factors that affect Sri Lanka’s economic development. Behind the economic logic lies the profound impact of the institutional，historical，social and external environment on Sri Lanka’s economic development model and development path dependence. At present，the growing comprehensive economic crisis is not only negatively affecting Sri Lanka’s economic development，social welfare and national image，but also undermining the country’s social and political stability，and may even lead to the rise of populism and greater geopolitical competition risks.