In this research we investigated the physico-mechanical properties and thermal stability of chlorosulfonated polyethylene (CSM) rubber, filled with nano- and micro-silica particles content ( 5-20 phr) prepared using base formulations. The mixing of rubber compounds was carried out in a two roll mill. The mixing time was 20 min. The vulcanization was carried out in an electrically heated laboratory hydraulic press at 155°C during. The physico-mechanical properties like tensile strength, elongation at break, compression set, hardness and abrasion resistance have been studied. For all cure characteristics, the nano-silica filled samples have higher values than micro-silica, also samples with 5 phr micro silica particles and 15 phr of nano silica particles, have higher values than all samples for cure characteristics. Results show that in the samples with 5 phr micro silica particles and 15 phr of nano silica particles added to the polymeric matrix, the ultimate tensile strength (UTS) were 8.1% and 43.2% higher than the reference sample respectively. Increase of the nano- and micro- silica particles concentration led to decrease in the abrasion resistance of the samples. The hardness, modulus increases with increasing nano and micro-silica loading and have higher values for nano silica filled samples.The result of swelling test showed that increase of the nano- and micro-silica loading filler led to increase of crosslink density. Also SEM images of the latest samples showed that the agglomeration of the filler particles and voids in the polymeric matrix were slight compared to other samples. The swelling test and SEM images confirmed the results mentioned above. In the continuation of our study we investigated the effect of adding 5-15 phr of nano- silica particles, on the physico-mechanical properties in the hybrid samples containing 5 phr micro- silica particles. The ultimate tensile strength of 5 m/ 5 n ( 5 phr nano- silica / 5 phr micro- silica particles) sample was 27.4% higher than reference sample. In the next step, we prepared two samples, each containing 15 phr nano-silica particles which were surface modified 50% and 100% respectively. Thermogravimetric analysis (TGA) results showed that the 10% mass loss temperatures of the three samples containing 5 phr micro silica particles, 15 phr of nano silica particles and different ratios of hybrid filler( 5 phr nano- silica / 5 phr micro- silica particles) ,were 52.2, 9.3 and 1.5?C respectively. Weight precent of the remainder of these three samples were 23.3,15.5 and 18.1% respectively. While the weight precent of the remainder of reference sample was 12% . The sample containing 15 phr nano silica particles has been recognized as a sample with best properties and coated on a roller. Keywords: Chlorosulfonated polyethylene, CSM, nanosilica, abrasion resistance, mechanical properties, thermal resistance.