To deal with the problem that the localization result of Distance Vector-Hop (DV-HOP) may be rendered far from precision by the Sybil attack in Wireless Sensor Network (WSN), two hop difference based secure localization algorithms, namely HDDV-HOP and EHDDV-HOP, were proposed. Firstly, neighbor node lists of other nodes were got by the detection nodes through the controlled flooding mechanism. Secondly, the neighbor node lists were analyzed to detect fake nodes and white node lists were established. Finally, packets were selectively relayed based on white node lists and the unknown nodes were securely localized. The two algorithms differ in the techniques they used to detect fake nodes. In HDDV-HOP, whether or not neighbor node lists were the same was checked; while in EHDDV-HOP, the ratio of the amount of elements in the intersection of two neighbor node lists to that of elements in the union of the two was analyzed. The simulation results show that, compared with DV-HOP without the Sybil attack, when the ratio of beacon nodes to normal nodes reaches 20% and signal coverage is asymmetric,the localization error of HDDV-HOP is increased by 133.4%, while the error of EHDDV-HOP is increased by 7.3% when the similarity threshold is suitable, but the localization errors of the both algorithms are smaller than that of DV-HOP with the Sybil attack. Both of HDDV-HOP and EHDDV-HOP can defend against the Sybil attack, however EHDDV-HOP outperforms HDDV-HOP.