Objective To study the changes of detrusor microvessel density and apoptosis related factor PCNA and Bax in different phase of partial bladder outlet obstruction. Methods Forty Wistar rats were divided into control(n =10), sham-operation(n =10) , two-week obstruction( n = 10) and five-week obstruction group(n = 10). The expression of detrusor microvessel density and apoptosis related factors PCNA and Bax were evaluated with immunohistochemistry method. Results The average weight of bladder was (125.5?10. 1) ,(128.5?8.9) ,(380.0?12.4) ,(400.0?12.5) mg in control, sham-operation, two-week obstruction and five-week obstruction group, respectively. The difference between control, sham-operation group and obstruction group was significant (P 0. 05 ) . The expression of microvessel density was 2. 1?1.3,13.3?2.3,36.4?4. 1 and 37.3?5.6 in control, sham-operation, two-week obstruction and five-week obstruction group, respectively. The difference between control, sham-operation group and obstruction group was significant ( P 0. 05 ). The expression of PCNA was (38. 2?17. 2)% , (39. 4?11.4)% , (64. 1?11. 5)% and (46. 2?9. 6)% in control, sham-operation, two-week obstruction and five-week obstruction group, respectively. The difference between control, sham-operation group and obstruction group was significant (P