The article considers the state budget deficit as a key indicator of Ukraine’s budget security. The main threats of the state national security in the economic sphere, their preconditions and consequences, as well as the impact on the state of public finances and processes of external migration of the population are investigated. The role of the Pension Fund of Ukraine in the process of forming the state budget deficit of Ukraine is analyzed. It is proved that each of these threats is a systemic destructive phenomenon that negatively affects the state’s economy and has direct or indirect impact on public finances and, in particular, on the level of budget security. It is substantiated that an adequate level of budget security is a basis for the protection of national interests’ formation of Ukraine and sustainable development of the national economy. It is noted that the overall effect of the totality of all threats (latent, explicit, potential, direct and indirect) to the national security of Ukraine is quite clearly traced when analyzing the state of public finances in general and the nominal volumes and dynamics of changes in the state budget deficit as a percentage of GDP. It is determined that the calculations of indicators of Ukraine’s budget security assessment and comparison of obtained results with their normative values prove that there is a threat to the financial and economic system of the state due to large amounts of government debt and excessive amounts for their repayment and servicing. The main reasons for the deviation from optimal values of the level of redistribution of GDP through the consolidated budget, the ratio of total payments for servicing and repayment of public debt to state budget revenues as the most critical indicator of budget security. A set of measures for minimizing the negative impact of systemic threats in the economic sphere on the state of public finances and the level of national security of the state is proposed