diff --git a/sec-beidou-rtcm/src/main/java/com/imdroid/sideslope/calc/SingleLineGNSSCalcService.java b/sec-beidou-rtcm/src/main/java/com/imdroid/sideslope/calc/SingleLineGNSSCalcService.java
index b7a58a2a..b1388a08 100644
--- a/sec-beidou-rtcm/src/main/java/com/imdroid/sideslope/calc/SingleLineGNSSCalcService.java
+++ b/sec-beidou-rtcm/src/main/java/com/imdroid/sideslope/calc/SingleLineGNSSCalcService.java
@@ -283,7 +283,7 @@ public class SingleLineGNSSCalcService implements GNSSDataCalcService {
 
             //更新有效解时间
             if(locationRecord.getEnabled()){
-                if(device.getLastValidCalcDataTime().isBefore(resultTime)){
+                if(device.getLastValidCalcDataTime()==null || device.getLastValidCalcDataTime().isBefore(resultTime)){
                     device.setLastValidCalcDataTime(resultTime);
                 }
             }