A building toy block set consisting of base blocks and connection blocks is disclosed. Each base block has a connection notch located on each of multiple peripheral sides thereof and extending in direction toward the center thereof, and two pivot holes arranged at two opposite lateral sides of each connection notch. Each connection block has two pivot pins respectively located on two first opposing sides thereof and respectively pivotally connectable to the pivot holes at two opposite lateral sides of one connection notch of one base block, and a plug rod and a plughole respectively located on two second opposing sides thereof in such a manner that the plug rod of one connection block can be press-fitted into the plughole of another connection block.