Recently, there have been several cracking failures of type HL carbon steel sucker rods with evidence of fatigue striation. In order to find out the reason for the fracture failure, the fracture morphology, material properties, loading and corrosion product of the failed type HL 35CrMoA sucker rod were analyzed, combined with the corrosion environment. The results show that the material properties of the failed 35CrMoA sucker rod meet the GB/T 26075-2010 standard requirements. Also the result of loading analysis shows that the loading is far from the fatigue limit stress. The type HL sucker rod’s yield strength is almost 1049 MPa and hardness is 35.2 HRC. In addition, the low in-situ pH and high H2S-CO2 partial pressure places the sucker rods in the Region 3 of sulfide stress corrosion cracking, which means the quenched and tempered sucker rod’s yield strength should not exceed 863 MPa and hardness should not exceed 30 HRC, according to the ISO 15156-2:2015 standard. It is concluded that the high hardness level of the type HL sucker rod led to sulfide stress corrosion cracking in the high H2S-CO2 partial pressure and low in-situ pH condition.