Crystalline silicon solar cells with SiNx/SiNx and SiNx/SiOx double layer anti-reflection coatings(ARC) were studied in this paper. Optimizing passivation effect and optical properties of SiNx and SiOx layer deposited by PECVD was performed prior to double layer application. When the refractive index (n) of silicon nitride was varied in range of 1.9∼2.3, silicon wafer deposited with silicon nitride layer of 80 nm thickness and n= 2.2 showed the effective lifetime of 1,370 ㎛. Silicon nitride with n= 1.9 had the smallest extinction coefficient among these conditions. Silicon oxide layer with 110 nm thickness and n= 1.46 showed the extinction coefficient spectrum near to zero in the 300∼1,100 nm region, similar to silicon nitride with n= 1.9. Thus silicon nitride with n= 1.9 and silicon oxide with n= 1.46 would be proper as the upper ARC layer with low extinction coefficient, and silicon nitride with n=2.2 as the lower layer with good passivation effect. As a result, the double layer AR coated silicon wafer showed lower surface reflection and so more light absorption, compared with SiNx single layer. With the completed solar cell with SiNx/SiNx of n= 2.2/1.9 and SiNx/SiOx of n= 2.2/1.46, the electrical characteristics was improved as ΔVoc= 3.7 mV, ΔJsc= 0.11 mA/cm2 and Δ Voc= 5.2 mV, ΔJsc= 0.23 mA/cm2, respectively. It led to the efficiency improvement as 0.1% and 0.23%.