The invention discloses a control method of a flocculation washing machine. The control method includes the steps that the washing water amount V and the washing-agent putting amount m in the washing procedure are obtained and detected respectively to obtain the washing-agent concentration C which is the quotient of m and V; according to the washing-agent concentration C, the number N of flocculation cycle times of washing water and the flocculating-agent putting amount Mn corresponding to all flocculation cycles are determined. In the control method, the number N of the flocculation cycle times and the flocculating-agent putting amount Mn corresponding to all the flocculation cycles can be accurately obtained only through the parameter of the washing-agent concentration in the washing procedure, and accurate controlling for the washing-machine flocculation treating process is achieved; meanwhile, flocculation treatment and the rinsing procedure of the washing machine are synchronously carried out, and when the washing machine is in the ending node, the concentration of a washing agent in an outer barrel is lower than a preset value accordingly to achieve the aim that the residual washing agent on cloth is removed. The invention also discloses the washing machine in which the control method is used.