Dyeing wastewater released from dye-utilizing industries containing numerous hazardous dyes poses serious threat to environment and human beings, thus removal of dyes from wastewater is an important issue. In current work, guanidinium functionalized cellulose (GFC) was prepared by radiation emulsion grafting glycidyl methacrylate onto cellulose followed by further modification with guanidine hydrochloride. The radiation grafting and modification conditions were optimized. The GFC used for dyes removal was obtained with grafting yield of 238% at dose of 20 kGy and guanidinium group (%) of 16.49%. The adsorption behaviors towards methyl orange (MO) and acid fuschin (AF) were investigated. Adsorption kinetics was well described by pseudo-second-order kinetic mode. The adsorption isotherm was well fitted with Langmuir isotherm model. The adsorption capacity for MO and AF reached 63.25 mg/g and 120.4 mg/g, respectively. Therefore, the GFC exhibited excellent adsorption performance, which was applicable for MO and AF removal of water treatment.