<正>Objective: To investigate the association between the diversity of urease gene and urease activity of clinical isolates of Helicobacter pylori （H. pylori）. Methods: Polymerase chain reaction-restriction fragment length polymorphism （PCR-RFLP） of urease gene and rapid urease activity test were used to study the urease activity of different clinical isolates of H. pylori. Results: H. pylori clinical isolates were divided into 4 types according to their PCR-RFLP results of urease gene and urease activity. Type Ⅰ

possessing strong urease activity （0. 11） and presented 1 fragment of 1. 7 kb by PCR-RFLP

had close relations with gastric ulcer; type Ⅱ

with the weakest urease activity （0. 07） and 2 fragments （1. 3 and 0. 4 kb respectively）

was associated with duodenal bulb ulcer; type Ⅲ

with the strongest urease activity （0. 12） and 2 fragments （0. 4 and 0. 17 kb） with or without 1 fragment （0. 23 or 0. 37 kb）

was responsible for gastritis; type Ⅳ

with weak urease activity （0. 09） and 2 fragments