High cellulase producing Streptomyces strain C188 was isolated from a Saudi Arabia soil sample and identified as Streptomyces longispororuber by 16S rDNA sequencing. Enzyme productivity by this strain in carboxymethyl cellulase liquid medium reached 8540 U/L after 96 h of incubation at 30°C. Cellulase productivity in tested strain was improved (25084 U/L) by supplementation of the carboxymethyl cellulase liquid medium with 1% corn steep liquor and pH 6.5 (maintained throughout the incubation period using 0.05 M phosphate buffer). Purification of cellulase enzyme was carried out by ammonium sulfate precipitation, diethylaminoethyl cellulose and Sephadex G-75 gel filtration chromatography. The final preparation had 13.5% activity recovery and approximately 38.5-fold purification. The purified enzyme migrated in a single band with molecular weight of 42 kDa on SDS-PAGE. Maximum enzymatic activity was observed at pH 6-6.5 and 50°C, while maximum stability was obtained at pH 6.5 and up to 60°C.