Daqing oilfield has entered the late stage of development, and the work of hot cleaning and paraffin prevention is faced with many problems. In order to solve the problem that the reverse pressure production and hot washing can not reach the expected wax removal effect during the washing process of the pumping unit well, the analysis and calculation method of the reverse washing and productivity recovery process of the machine production well are studied. According to the change of dynamic fluid level during well washing, the dynamic equation of inflow of backflow is established, and the numerical value of inflow of backflow during and after well washing is calculated by using definite integral operation and combining with the field production parameters of the oil well. At the same time, according to the calculated amount of backflow, the capacity recovery time is calculated by integrating. Scientific calculation of #1 backfilling volume (45 m3) and capacity recovery time (69 h), improve the actual withholding time (24 h). For the backflow pumping unit, the well washing protector is applied to avoid the washing fluid from entering the oil reservoir, achieve the purpose of protecting the oil reservoir and shortening the production recovery time. The field test applies 5 Wells, and each well washing time can reduce the impact of 0.84 t of crude oil and create an additional benefit of 2000 yuan. It provides technical support and guarantee for the work of hot cleaning and wax prevention in the future, and improves the way of withholding production, effectively solves the phenomenon of oil well backflow, and increases crude oil production.