Method for compressing bitmap indexes

The invention discloses a method for compressing bitmap with an aim to provide the method for improving encoding rate of the bitmap indexes. The method includes: dividing bit sequences into groups taking 31 bits as a unit, wherein the groups include two categories of F-groups and L-groups, the F-groups include 0-F-groups and 1-F-groups, the L-groups include two categories of C-L-groups and NI-L-groups, and the NI-L-groups include the NI-L-groups of 0-NI-L types and 1-NI-L types; merging group sequences of all the groups; encoding the merged group sequences. Compared with a compressing method in the prior art, the method has the advantages that the L-groups are further divided in type, encoding situation is expanded, and encoding rate is increased.