Objective To evaluate MR diffusion-weighted imaging (DWI)and MR perfusion-weighted imaging(PWI) in differentiating benign from malignant soft tissue tumors by comparing the related parameters. Methods Fifty patients with soft tissue tumors verified by pathology( benign 24, malignant 26) underwent DWI and dynamic contrast-enhanced T2 * -weighted PWI. DWI and PWI data of benign and malignant soft tissue tumors were acquired at the workstation and their difference was analyzed with t-test. The diagnostic accordance rate was verified with x2-test. Subjective overall performance of two techniques were evaluated with receiver operating characteristic (ROC) analysis. Results ADC values of benign and malignant tumors were (2. 03±0. 36) × 10-3 mm2/s, ( 1.52±0. 39) × 10-3 mm2/s,respectively. The signal intensity decrease of them during the first-pass perfusion (SIdecrease ) were ( 13.54 ± 3.37 )%, (47. 57 ± 5. 21 ) % ,respectively. The maximum linearity slope rate of TIC ( SSmax ) of them were ( 5.51 ± 2. 54 ) %, (7.94 ± 3. 33) %, respectively. There were significant differences between benign and malignant tumors of ADC value and SIdecrease ( t = 2. 515,2. 938 ;P < 0. 05 ), while there was no significant difference in SSmax (t = 1. 272,P >0. 05). When the threshold of ADC value was 1. 866 × mm2/s, sensitivity and specificity for determining malignant tumors were 84. 6% (22/26)and 83.3% (20/24). When the threshold of SIdecrease was 40. 33% ,sensitivity and specificity for determining malignant tumors were 88. 5% (23/26)and 75.0% (18/24). In type Ⅰa of TIC,the proportion of benign soft tissue tumor was 3/24 and malignant tumor was 20/26. In type Ⅰb , benign tumor was 14/24 and malignant tumor was 3/26. In type Ⅰc, malignant tumor was 3/26. In type Ⅱ ,benign tumor was 7/24. The diagnostic accordance rate of DWI and PWI were 84. 0% (42/50) and 82. 0% (41/50), respectively. There was no significant difference between them ( x2 = 0. 8, P >0. 05). The accuracies of them were 81.7% , 83. 6% respectively by the area under the ROC curve (AUC). The sensitivity of PWI in diagnosing malignant soft tissue tumors was higher. Conclusions ADC value and SIdecrease are Valllable diagnostic parameters in differentiating benign and malignant soft tissue tumors. The threshold of these parameters for diagnosing malignant soft tissue tumors are 1. 866 × 10-3 mm2/s and 40. 33%, respectively. The type of TIC can help to distinguish malignant tumors from benign tumors, while the SSmax can not. The accuracies of DWI and PWI in the diagnosis of malignant soft tissue tumors are moderate. Compared with DWI, PWI should be selected firstly because of its higher sensitivity in diagnosing malignant tumors.