The present invention relates to a connection system for connecting component sections of wind turbine blades, according to which one or more intermediate parts (2) formed by a complex structure defining end transverse partitions (2.1) and a central transverse partition (2.2), between which there extend columns (2.3) separated by openings (2.4), is arranged between the blade sections (1) to be connected, the openings (2.4) including short bolts or screws (3) that pass directly through the end transverse partitions (2.1) and long bolts or screws (3) that pass inside the columns (2.3), said bolts or screws (3) being screw-coupled to nut-like anchoring parts (4) housed in the material of the blade sections (1).