In this study, the thermo-gelation behavior of hydroxypropyl methylcellulose (HPMC) and hydroxyethyl methylcellulose (HEMC) were examined by rheology. Temperature sweep shear viscosity measurements revealed a significant decrease in the shear viscosity of HPMC and HEMC at the aggregation temperature (Tagr), which depended on the substitution type (HPMC or HEMC) and degree of substitution. In the dynamic test, G’ decreased slightly at Tagr and increased significantly at the gelation temperature (Tgel). The shear viscosity and shear storage modulus (G’) can be utilized complementarily to examine Tagr and Tgel. Tagr could be detected clearly by the shear viscosity measurement but could not be observed in the G’ measurement. On the other hand, Tgel could not be detected in the shear viscosity measurement although it can be clearly recognized in G’ measurement. Conclusively, the two rheological measurements could be utilized complementarily in detection of Tagr and Tgel. In the meanwhile, HPMC with more hydrophobic residues (methoxy and hydroxypropyl residues) showed smaller Tagr and Tgel than HEMC, which has hydroxyethyl and methoxy groups. Tagr and Tgel decreased with increasing number of hydrophobic groups. Molecular weight almost did not affect Tagr and Tgel of HPMC solution.