Superconductivity and crioelectronics were subjects of his research.
He was head of many national progects, some of them with the government department of defence.
In the field of scientific instrumentation, he designed and created more than 30 apparatuses.
A. Spassov was head of the research group on nonlinear phenomena in the Institute of Electronics at the Bulgarian Academy of Sciences (1972 – 1990)
He founded and headed Laboratory of Cryogenic and Superconducting Electronic (1990 – 2002)
He was Institute of Electronics deputy director (1973 – 1978) and director more than 15 years (1978 – 1993)
He headed Institute of Microelectronics too (1979 – 1986)