Controllable preparation of inorganic nanomaterials with specific morphology and structure is very important for their applications in various fields. Herein, a general strategy was proposed to controllably synthesize nano-CaCO3 via a water-in-oil microemulsion method in the rotating packed bed reactor. By tuning key parameters, nano-CaCO3 with four primarily analyzed morphologies, including spherical, spindle-like, clustered, or linear formations, can be selectively obtained. The diameters of the nanospheres are adjustable within the range of 4-20 nm, and the lengths of the nanowires can be tuned from 100 to 800 nm. Notably, nano-CaCO3 with four crystal forms, amorphous, vaterite, aragonite, and calcite, can also be controllably synthesized. Importantly, these prepared nano-CaCO3 have excellent dispersity, which can be well-dispersed in dozens of types of liquid media to form transparent or semitransparent nanodispersions. This work provides a general method for producing nanomaterials, enabling precise control over the desired morphology and structure and ensuring commendable dispersibility, which can greatly foster broader preparations and applications of nanomaterials in the fields.