The influence of hot stretching ratio and stretching temperature on the connecting bridge structure formed during the fabrication of polypropylene microporous membrane was studied. It was found that with the increase of stretching ratio to 200 % under temperature of 130 A degrees C, bridge length was increased. Under the stretching ratio of 100 %, the main melting peak became wider, whereas similar phenomenon could not be seen under temperature of 110 A degrees C. Under the ratio of 200 % and temperature of 130 A degrees C, strong bridge structure lead to appearance of small shoulder on the right of main melting peak. Compared with that only through cold stretching, more connecting bridges were initiated during hot stretching. The unrestrained tie chains due to the chain disentanglement under high temperature, which were not involved in the annealing crystallization and cold stretching, could be stretched and crystallized into bridges. At the same time, some chains could also be pulled out from the initial lamellae. All these contributed to the increase of bridge number. During hot stretching, the broken bridges merged with other stable bridges and some bridges adhere to each other, resulting in the formation of stable bridges, which will be helpful to the stabilization of pore structure.