The corrosion behavior of 20# steel in oilfield production fluid was studied by corrosion weight loss method, tow electrode technology and electrochemical measurement technology. The results show that the corrosion development process can be divided into the initial corrosion stage, the corrosion development period and the corrosion stability period during the experimental period. The corrosion is the most serious in the initial stage of corrosion. The polarity reversal of cathode and anode occurs at the same position of metal with the prolongation of experimental time, and as the temperature increases, the inversion period becomes shorter. Through the electrochemical measurement of the corrosion metal as a whole and in part, it is found that the types of corrosion occur at different temperatures and locations.