Based on the review of domestic and foreign researches on the shear failure mechanism of slender reinforced concrete beams without shear reinforcement, the basic assumptions, the key points and the calculation methods for shear strength of different models were introduced and commented, such as the modified compression field theory, the critical shear crack theory, the plasticity theory, the compressive force path theory, the splitting failure theory and the strain based shear strength model. Using the test data from the related experimental programs and the ACI-DAfStb shear database of slender beams, impact assessments of important design parameters and statistical evaluations were conducted on the calculation methods for shear strength of different models. Some points of view on expectation of shear failure were presented. The results showed that the absences of direct experimental proofs of some hypotheses were apparent and different opinions on the shear transfer contribution of diagonal tension (splitting), shear (aggregate interlock) and the flexural compression zone were the main divergence of the shear transfer mechanism. Further improvements in the rationality of the considerations for different factors and the accuracy of the calculation methods for shear strength were essential. In subsequent research work, the random and physical characteristics of shear failure should be considered synthetically. Advanced testing technology and analysis of the evolution of the stress field can be utilized in revealing the mechanism of shear failure.