Objective To observe the change of protein levels of large conductance calcium activated potassium channel (BK‐Ca) in placental arteriole smooth muscle cells from hypertensive disorder complicating pregnancy and discuss its role .Methods Western blot analysis was used to examine protein expression of α subunit andβ1 subunit of BKCa channels in placental arteriole smooth muscle cells from hypertensive disorder complicating pregnancy .Results The relative protein expression level of α‐subunit in the HDCP group was 1 .001 2 ± 0 .169 8(n=15) ,and the NT group was 1 .028 2 ± 0 .180 6 (n=15) .There was no significant differences between the two groups (P> 0 .05);the relative protein expression level of β1 subunit in the HDCP group was 0 .418 1 ± 0 .080 8 (n=15) ,and the NT group was 1 .616 8 ± 0 .012 6 (n=15) ,theβ1‐subunit protein expression levels of HDCP group were significantly lower (P<0 .05) .Conclusion The protein expression ofβ1‐subunit ,but notα‐subunit ,was reduced in pla‐cental arteriole smooth muscle cells from hypertensive disorder complicating pregnancy .Therefore ,BKCa channel activity may have been involved in hypertensive disorder complicating pregnancy ;and the abnormal expression ofβ1 subunit maybe an important basis in hypertensive disorder complicating pregnancy .