OBJECTIVE： To compare effects and safety of ultrasound-guided transabdominis plane block （TAPB） of different concentrations of bupivacaine on related indexes in patients after appendectomy. METHODS： Totally 120 appendicitis patients selected from our hospital during Mar. 2017-Mar. 2018 were randomly divided into group A， B， C， D， with 30 cases in each group. All patients received ultrasound-guided TAPB immediately after surgery. Group A was given 0.35％ bupivacaine 20 mL intravenously； group B was given 0.25％ bupivacaine 20 mL intravenously； group C was given 0.15％ bupivacaine 20 mL intravenously； group D was given 0.9％ Sodium chloride injection 20 mL intravenously， and then given patient controlled intravenous analgesia. The VAS scores of 4 groups in resting and cough state were recorded at 2 h（T1）， 4 h（T2）， 8 h（T3）， 12 h（T4）， 24 h（T5）， 48 h（T6） after ultrasound-guided TAPB. Satisfaction degree of postoperative analgesia， the rate of tramadol use， press times of analgesic pump， anal exhaust time， the time of getting out of bed and the occurrence of ADR were observed in 4 groups. RESULTS： At T2-T5， VAS scores of 4 groups in resting were significantly lower than same group at T1 and T6； at T3， VAS scores reached the highest value and then decreased gradually， with statistical significance （P＜0.05）； there was no statistical significance at T1 and T6 （P＞0.05）. At T1-T6， VAS scores of group A， B and C were significantly lower than group D， with statistical significance （P＜0.05）； there was no statistical significance among group A， B and C （P＞0.05）.  At T2-T4， VAS scores of 4 groups in cough state were significantly higher than same group at T1； at T3 and T4， VAS scores reached the highest value （group D at T4）， at T5-T6， VAS scores were lower than same group at T1； at T1-T6， VAS scores of group A， B and C were significantly lower than group D， with statistical significance （P＜0.05）， but there was no statistical significance among group A， B and C （P＞0.05）. The score of analgesia satisfaction degree and the case number excellent analgesia satisfaction degree in group A， B and C were significantly higher than or more than group D； utilization rate of tramadol and press times of analgesic pump were significantly lower than or less than group D， with statistical significance （P＜0.05）. There was no statistical significance among group A， B or C （P＞0.05）. There was no statistical significance in panal exhaust time， the time of getting out of bed， the incidence of nausea and vomiting， dizziness， pruritus or retention of urine among 4 groups （P＞0.05）. No local anesthetic related toxic reaction occurred in each group. CONCLUSIONS： After appendectomy， ultrasound-guided TAPB of different concentrations of bupivacaine have similar analgesic effect and safety. Considering high risk of toxic reation induced by high concentration of bupivacaine， low concentration as 0.15％ bupivacaine is more suitable.