A modularized fishing reel spool comprises a drag adjust knob, a brake device having two springs and washer stacks, a front lid, a core and a skirt. A turning support system of the spool comprises a two bearing system, a main shaft and a core shaft. Compared to conventional fishing reel spools, this invention provides a spool having advantages such as better structural design, wider adjustable brake range, superior line-loading force application, well-functioned water drainer system, low manufacturing cost and lower material usage.