Social security needs to be combined to calculate the length of service.

Legal analysis: It can be combined, provided that the unit must pay social insurance in full during the working period, so the years from the original unit to the present unit can be regarded as the years of insurance payment. If the calculation is combined, it can be obtained from the original unit and handed over to the social security institution that pays first.

Legal basis: People's Republic of China (PRC) Social Insurance Law.

Article 1 This Law is formulated in accordance with the Constitution for the purpose of regulating social insurance relations, safeguarding citizens' legitimate rights and interests in participating in social insurance and enjoying social insurance benefits, enabling citizens to share the fruits of development and promoting social harmony and stability.

Article 2 The state establishes social insurance systems such as basic old-age insurance, basic medical insurance, industrial injury insurance, unemployment insurance and maternity insurance, so as to guarantee citizens' right to receive material assistance from the state and society in accordance with the law in case of old age, illness, industrial injury, unemployment and maternity.

Article 3 The social insurance system adheres to the principles of wide coverage, basic protection, multi-level and sustainability, and the level of social insurance should be compatible with the level of economic and social development.

Article 4 Employers and individuals in People's Republic of China (PRC) shall pay social insurance premiums according to law, and have the right to inquire about payment records and personal rights and interests records, and ask social insurance agencies to provide social insurance consultation and other related services. Individuals enjoy social insurance benefits according to law and have the right to supervise the payment of their own units.