The ensemble based variational method (EnVar) is used to study a retrievable problem about turbulence viscosity coefficient in the atmospheric boundary layer EK model.By using the EnVar, the gradient expression of the cost function in retrieving turbulence viscosity coefficient is deduced, and the retrievable calculation solutions are given. A series of ideal numerical experiments are conducted on the retrieving of turbulence viscosity coefficient. The results of numerical experimentations show that it is successful to use the EnVar to retrieve the turbulence viscosity coefficient in the EK model. In addition, through adjusting ensemble number, initial disturbance mean variance, and initial value appropriately, the inversion precision can be further enhanced. It is feasible to use the EnVar to retrieve the parameter of atmospheric boundary layer.