Abstract: As the expansion of area of protected field and the increasing year of cultivation, the supply of silicon in soil is probably insufficient. Silicon plays a key role in enhancing resistance, improving fruit quality and protecting from disease and pest. So far, there is no systematic determination method of available silicon in northern glebe of China. Soil samples were collected from protected field with different cultivation year, available silicon was extracted by several convention methods and the comparison of the results and its relationship with soil chemical properties were studied. The results show that there was clear difference in content of available silicon extracted by different methods, but there was positive correlation between them. The analyses of regression show that available silicon extracted by different methods in soil was relevant with soil pH, EC and soil depth. The results will be useful for silicon research for the future.