Objective: To observation the dynamic circadian fluctuations of the blood pressure in unbonded spontaneously hypertensive rats using Telemetry technology. Method: Taking eight 3-month-old SPF SHR rats, there were implanted C50-PXT device intraperitoneally. Seven days later, monitoring chainless blood pressure for 24 h continuously time using telemetry system. Analysing 24 h ambulatory blood pressure and blood pressure trend diagram used by EMKA analysis software. Result: Blood pressure and heart rate show the circadian rhythm changes in SHR rats of three months, moreover daytime is obvious lower nighttime(P<0.01).Blood pressure appear two periods of peaks at AM1:30-2:30 and PM8:30-9:30,appear low ebb at PM2:00-2:30.Thereinto average of systolic blood pressure is 166.02mmHg in nighttime,two peak of systolic blood pressure was 172.13mmHg and 171.38mmHg respectively. average of SBP is 162.73mmHg in daytime, valley bottom of SBP was 155.73 mmHg.But heart rates appear two periods of peaks at AM1:30-2:00 and PM8:00-9:00,peak value of heart rates were 375.00time/min and 373.26time/min respectively. Valley bottom of heart rates appear at AM 11 or so, bottom peak value of heart rates was 310.91time/min. Average of heart rates were 328.85 time/min and 346.05 time/min at the daytime and nighttime respectively. Conclusion: Blood pressure and heart rate show the circadian rhythm changes in SHR rats of three months. Blood pressure and heart rates appeared two peaks in the night，but was a low point at daytime.The average blood pressure and heart rate of daytime are lower than nighttime. Circadian Rhythm of blood pressure and heart rate was related with activities in SHR rats. Telemetry can accurately reflect blood pressure circadian rhythmicity in SHR rats, contribute to evaluation of antihypertensive drugs and the physiological mechanism of high blood pressure research correctly.