Objective To evaluate Left atrial function by real-time three-dimensional echocardiography （RT-3DE） and two-dimensional speckle tracking imaging （2D-STI） in patients with hypertrophic cardiomyopathy（HCM） .Methods Our work included 2 groups as HCM group，n=49 patients and control group，n=33 healthy volunteers. Left atrial maximal volume（LAVmax），left atrial minimal volume （LAVmin），left atrial presystolic volume（LAVpre） were calculated by RT-3DE.Then the Left atrial volume index（LAVI）was calculated by dividing the body surface area（BSA），and left atrial stroke volume（LASV），left atrial total ejection fraction（LAEF），left atrial passive ejection fraction（LAPEF），left atrial active ejection fraction（LAAEF） were calculated. Two-dimensional images were acquired from the apical four chamber view，two-chamber view and apical three-chamber view to retain images for offline analysis.The systolic，early and late diastolic peak strain rate （SRs，SRe，SRa）curves were acquired in each middle segment of left atrium（septal，lateral，anterior，inferior and posterior ） by 2D-STI.And the average strain rate was calculated （mSRs，mSRe，mSRa），then the differences of above parameters between the two groups were compared.Finally，the correlation analysis between LAEF and mSRs，LAAEF and mSRa，LAPEF and mSRe were performed.Results LAVImax，LAVImin，LAVIpre were increased in HCM group than normal group，meanwhile LAEF and LAPEF were decreased. SRs of left atrial wall except inferior，mSRs，SRe of left atrial wall，mSRe，SRa of left atrial wall and mSRa were reduced compared with normal group（P＜0.05）.There was a positive correlation between mSRe and LAPEF，mSRa and LAAEF，and between mSRs and LAEF （r=0.608，0.314，0.396，P＜0.05）.Conclusions RT-3DE combined with 2D-STI can accurately determine the left atrial volume in patients with HCM，and the compensatory effects of left atrial pump function，conduit function and reservoir function are weakened or disappeared，which has a good clinical application value.