What is the base year of industrial production index?

The current base year of the industrial production index is 2011-12. The earlier base years which were used for calculating the index of industrial production were 2004-05, 1993-94, 1980-81, 1970,1960, 1956, 1951, 1946, 1931. You can read about the Index of Industrial Production [UPSC Economy Notes] in the given link.

Further readings:

1. Merger of NSSO and Central Statistical Office (CSO) to form National Statistical Office (NSO)
2. Core Sectors of the Indian Economy