This paper presents design of a microwave sensor based on circular split ring resonator (SRR) and coplanar waveguide (CPW) transmission line with two ports. The proposed sensor is used to measurement dielectric constant characteristics for different dielectric materials. The overall dimensions of the proposed sensor configuration are of 30x 30 mm2. The measurement parameter is the transmission coefficient (S21). When the material under tested (MUT) is placed over the split ring resonator, the transmission coefficient resonance shifts. Rogers (RO3210) substrate material with dielectric constant of 10.2 and height of 1.27 mm is utilized as substrate for the proposed sensor. The resonance frequency of the proposed circular SRR sensor is 5.33 GHz. For suggested sensor, there is a non-linear relationship between the dielectric constant and resonance shift. The dielectric constant is predicted using the non-linear equation, and a good coefficient of determination is achieved.