The factors that have obvious effects on spatial variability at the different scales were identified with joint multifractal, and pedotransfer functions of van Genuchten model parameters which considered scale effect at small and large scale were established based on the above educed conclusion, furthermore, feasibility that concluded and educed at small scale with joint multifractal and applied at large scale was explored. The results showed that root mean square error of forecasted soil water content based on pedotransfer functions of van Genuchten model parameters in 0~20cm and 20~40cm soil layers at small scale was 0.0386 and 0.0473 respectively, and RMSE of forecasted soil water content based on pedotransfer functions of van Genuchten model parameters in 0~20cm and 20~40cm soil layers at large scale was 0.0270 and 0.0304 respectively; conclusions educed at small scale with joint multifractal could be applied at large scale, and pedotransfer functions based on these conclusions had strong theoretical foundation and high precision.