A method for transmitting a vehicle-to-everything, V2X, message by a User Equipment, UE, in a wireless communication system, the method comprising: Performing a candidate resource exclusion operation based on physical sidelink shared channel-reference signal received power, PSSCH-RSRP, threshold value in a selection window; determining whether a ratio between remaining candidate resources in the selection window and total of candidate resources in the selection window is smaller than a configured threshold value; based on the ratio being smaller than the configured threshold value, increasing the PSSCH-RSRP threshold value and re-performing the candidate resource exclusion operation based on the increased PSSCH-RSRP threshold value, according to whether at least one of latency requirement and priority of the V2X message satisfies a condition; and transmitting the V2X message by using a selected resource among candidates remained in the selection window, wherein the condition is that the latency requirement of the V2X message is shorter than a configured threshold value or that the priority of the V2X message is higher than a configured threshold value, and wherein: i) based on the ratio being smaller than the configured threshold value, and the V2X message not satisfying the condition, the PSSCH-RSRP threshold value is increased and the candidate resource exclusion operation based on the increased PSSCH-RSRP threshold value is re-performed, and ii) based on the ratio being smaller than the configured threshold value, and the V2X message satisfying the condition, the PSSCH-RSRP threshold value is not increased and the candidate resource exclusion operation based on an increased PSSCH-RSRP threshold value is not re-performed. Performing a candidate resource exclusion operation based on physical sidelink shared channel-reference signal received power, PSSCH-RSRP, threshold value in a selection window; determining whether a ratio between remaining candidate resources in the selection window and total of candidate resources in the selection window is smaller than a configured threshold value; based on the ratio being smaller than the configured threshold value, increasing the PSSCH-RSRP threshold value and re-performing the candidate resource exclusion operation based on the increased PSSCH-RSRP threshold value, according to whether at least one of latency requirement and priority of the V2X message satisfies a condition; and transmitting the V2X message by using a selected resource among candidates remained in the selection window, wherein the condition is that the latency requirement of the V2X message is shorter than a configured threshold value or that the priority of the V2X message is higher than a configured threshold value, and wherein: i) based on the ratio being smaller than the configured threshold value, and the V2X message not satisfying the condition, the PSSCH-RSRP threshold value is increased and the candidate resource exclusion operation based on the increased PSSCH-RSRP threshold value is re-performed, and ii) based on the ratio being smaller than the configured threshold value, and the V2X message satisfying the condition, the PSSCH-RSRP threshold value is not increased and the candidate resource exclusion operation based on an increased PSSCH-RSRP threshold value is not re-performed.