The evacuation routes which are selected by crew will affect their evacuation efficiency when an offshore platform under emergency conditions. To quantify the influence of evacuation route selection on crew evacuation efficiency, two scenarios are considered: Scenario1 is that crew independently select the evacuation routes to evacuate to the assembling point, Scenario 2 is that crew evacuate to the assembling point in accordance with the prescribed evacuation routes. The evacuation efficiency of these two evacuation scenarios is analyzed and discussed from the aspect of evacuation time, waiting time index (WTI), optimal performance statistic (OPS), mean non-flow statistic (MNS) and casualty, respectively. It is found that the evacuation time of crew in Scenario 1 reaches 255.09 s, but Scenario 2 is 32.84 s shorter. By analyzing the WTI of each evacuation exit in these two evacuation scenarios, a large number of people in Scenario 1 are congested at the exit 1, which is the main reason for the increase of evacuation time of Scenario 1. Moreover, the comparison of the OPS and MNS of these two evacuation scenarios indicates that crew in Scenario 1 have not made full use of evacuation exit resources and make it impossible for crew to reach the assembling points timely. Furthermore, in Scenario 1, there are ten crew unable to reach the primary assembling point in time. Scenario 2, however, suffers no casualties.