Objective To investigate the diagnostic value of intravenous pyelography and multi-slice spiral CT (MSCT) scanning for bladder cancer. Methods The clinical data and imaging of 82 patients with bladder cancer who were treated in our hospital from August 2015 to May 2018 were retrospectively analyzed. According to the data, all patients underwent intravenous pyelography and MSCT after admission. The imaging features of bladder cancer in different examination were analyzed, and the diagnostic accuracy of different examination for bladder cancer was summarized and compared. Results 82 patients with bladder cancer had 154 lesions in total, the detection rate of lesions by intravenous pyelography was 80.52%, the detection rate of lesions by MSCT was 97.40%, the correct diagnosis rate of bladder pyelography for bladder cancer was 67.44%, while the correct diagnosis rate of MSCT for bladder cancer is 93.02%.That is, the detection and diagnosis rate of bladder cancer by MSCT was significantly higher than that by intravenous pyelography (P<0.05). In the MSCT plain scan, patients with bladder cancer have a poor filling of bladder and thickening of the irregular bladder wall. In some patients, a mass shadow and a part of high-density shadow were observed in the bladder wall.Further enhancement of the scan showed that the mass had mild enhancement in the arterial phase, and persistent mild enhancement in the venous phase and the delayed phase. In the venous pyelography, the renal pelvis, renal pelvis and ureter are mainly shown, which can be shown with normalities, disappearance of the cup of the pelvis, hydronephrosis, expansion, etc., and poor filling of cyst and filling defects can also be shown. Conclusion Compared with intravenous pyelography, the detection and diagnosis rate of bladder cancer by MSCT is significantly higher, with better scanning effect and localization of diagnosis. It can more clearly show the histological structure of lesionsof bladder cancer, and thus is more favorable to provide strong evidence for clinical treatment