We designed a new plug flow reactor (NPFR) containing hematite powder in the forms of nano particles (bare and stabilized) and bulk suspended by air bubbles, without problems related to packed bed photoreactors (PBRs) to improve photocatalytic degradation of four different classes of dye in water in comparison with that of PBR. The real volume of NPFR (V-r) including the net volume of dye solution, without the dead volume of air bubbles (V-D), was determined to reach the maximum photodegradation (X-Max). The suspension increased the uniform distribution and effective surface of particles to contact to uv light in comparison with those of fixed bed in PBR, that this property improved due to decreasing their size in NPFR, too. X-Max. values using alpha-Fe2O3 NPs/pectin were more than those of other forms in NPFR with Vr values of 76.5, 70.2, 80.6 and 81.4 ml for removal of Methylene blue, Bismarck brown Y, Rhodamine B and Malachite green at 298 K, respectively using experimental volume of reactor of 94.2 ml. To have a PBR with the same conditions, Fe2O3 NPs with the mean size equal to that of alpha-Fe2O3 NPs/pectin used in NPFR, was used the Brunauer-Emmett-Teller method.