This study evaluates the filtration efficiency of a cabin filter and according filter media for fine particle (PM2.5) through laboratory tests and on road tests. Two testing system for the filter media test and filter tests were designed according to the international standard (EN1822 and ISO 11155).On road tests were completed on the real roadway conditions. In cabin particle concentration and ambient particle concentration was gotten by DustTrak(TSI). And then the filter efficiency was calculated according to the I/O ratio. The results showed the filter media’s efficiency was highest, compared the lowest efficiency of filter total efficiency. The real particle removal total efficiency on road was higher than the laboratory test result. According to the experiment data, the on road testing results (particle reductions) are approximately equal to geometrical mean of filter media efficiency and filter total efficiency.