For the reason that the critical thermal maximum(CTMax)is an excellent index for evaluating the thermal tolerance,we assessed the impact of different acclimation temperatures(24,28,32 ℃)and heating rates[(1±0.2)℃/h and (1±0.2)℃/min] on the CTMax values firstly.And then we compared the difference of the thermotolerance between the two morphologically similar varieties of juvenile kuruma shrimp Marsupenaeus japonicus(Bate,1888)by the CTMax values and the acclimation response ratio(ARR)values,and at the same time,the different distribution,the physiological traits of the oxygen consumption rate,suffocation point and temperature coefcient(Q₁₀)of the two varieties were analysed to explore their thermal tolerance mechanism.The results are as follows:(1)Significant effect was found on the CTMax values of the shrimps by different heating rates and acclimation temperatures(P<0.05).(2)At the acclimation temperature of 32 ℃,the CTMax value of variety Ⅱ was greater than that of variety Ⅰ(P<0.05)and the ARR values of variety Ⅱ were also greater than variety Ⅰ at all temperature intervals.(3)When exposed to the same acclimation temperature,the oxygen consumption rate and suffocation point of the variety Ⅰ were greater than those of variety Ⅱ(P<0.05).(4)The temperature coefcient(Q₁₀)value of variety Ⅰ at the temperature interval of 28-32 ℃ was greater than that of 24-28 ℃,while the result of variety Ⅱ was quite the contrary,and there was a difference between the optimum temperature of the two varieties.The results obtained in this work showed that the CTMax values,oxygen consumption rate and suffocation point of the juvenile kuruma shrimp were influenced by different acclimation temperatures and the thermotolerance of variety Ⅱ which is mainly distributed in the South China Sea was stronger than that of variety Ⅰ which is distributed in the East China Sea and the northern part of the South China Sea.