Under the current environment of Wireless Senor Networks (WSN), security is always one of the topics that everyone discussed about. Because of the limitations of WSN¡¦s unique resource, this results in the security of WSN needs to especially consider the calculating ability, memory capacity, characteristics of wireless communication, limited battery power supply, etc. Random key pre-distribution (RKP) is the one of the key distribution that is developed for the sake of safe communication of WSN, the characteristic of RKP is that there must have at least one common pre-distributed key in the two independent nodes in order to compose a pair-wise key, so that the safe communication can be carried out. However, if the nodes are distributed in the loose environment, the numbers of neighbors would be lower due to the decrease of average node degree. Then the connectivity of the entire network would decrease because it is not easy for the RKP to establish the pair-wise key. This paper would set the improvement of the entire network¡¦s connectivity under the loose environment as the starting point to extend the RKP-DE that only considers one-hop neighbor information, and reverse the flow path of RKP-DE and propose RKP- DEinverse from the viewpoint of two-hop neighbor information. Then RKP-DE and RKP- DEinverse are merged and become a new method ¡V RKP- DEtwo_hop, so as to try to prove that we can raise the connectivity of the whole network effectively.