The present invention relates to an electrode active material slurry, which includes (a) an electrode active material, (b) a conductive agent, (c) a binder, (d) a solvent, and (e) a cellulose-based compound having a weight-average molecular weight (Mw) of 2,000,000 to 3,000,000, a degree of substitution of 1.0 to 1.2, and a viscosity (Brookfield viscometer, speed of 12 rpm) of 4,000 cps to 10,000 cps, and an electrode and a lithium secondary battery which include the same. Phase stability of the electrode active material slurry may be improved and battery characteristics may be improved by using the cellulose-based compound having molecular weight and degree of substitution within a specific range.