A banknote counting and detecting machine based on longitudinal banknote feeding comprises a frame, a case arranged outside the frame, a banknote entwisting device arranged on the frame, a banknote conveying device arranged downstream of the banknote entwisting device, and a detection device arranged on the upper portion of the banknote conveying device. The banknote entwisting device comprises a banknote entwisting wheel, a banknote receiving wheel, a banknote pressing wheel and a banknote blocking wheel, wherein the banknote entwisting wheel is arranged upstream of the banknote inlet of the frame, the banknote receiving wheel is arranged downstream of the banknote inlet of the frame, a banknote conveying belt is connected between the banknote entwisting wheel and the banknote receiving wheel, the banknote pressing wheel is arranged on the upper portion of the banknote conveying belt, the banknote blocking wheel is arranged downstream of the upper portion of the banknote receiving wheel, and a channel only allowing one banknote to pass through is formed between the banknote pressing wheel and the banknote conveying belt as well as between the banknote blocking wheel and the banknote conveying belt. The banknote conveying device comprises a banknote feeding wheel and a banknote discharging wheel. The banknote feeding wheel, the banknote discharging wheel and the banknote receiving wheel are arranged in the same horizontal line. The banknote counting and detecting machine based on longitudinal banknote feeding has the advantages of being simple in structure, reasonable in design, good in banknote entwisting effect, high in banknote counting efficiency, capable of authenticating banknotes of different currencies and the like.