Objective: To explore a method of extracting tumor interstitial fluid (TIF) which is similar to muddy phlegm in Chinese medicine (CM), interleukin-8 (IL-8) in concentration was taken as the representative of the content of TIF, analyzed in the extracted TIF and the original tumor tissue, and examined to see whether TIF has an interfering effect on tumor recurrence. Methods: Tumor tissue was ground, centrifuged, and filtered for intercellular substances. Tumor-bearing Kunming S180 mice were raised for 21 days and then the tumors were removed to observe the influence of intervention with TIF, normal saline (NS) and a blank control on tumor recurrence. Results: The content of IL-8 in the filtered and unfiltered tumor tissue was not significantly different (P>0.05). Postoperative tumor recurrence in TIF intervention group was significantly higher than that in the NS intervention and control groups (60%, 12/20 vs. 20%, 4/20 vs. 15%, 3/20, χ2=11.058, P<0.01). Tumor cells grew vigorously and infiltrated to muscular tissue in TIF intervention group. Large numbers of tumor cells were seen necrotic in the NS intervention group, and small numbers of tumor cells were seen necrotic in the blank control group. Conclusions: TIF can be effectively extracted by the means described. It does not contain tumor cells, but its contents such as IL-8 may stimulate tumor cell growth and promote postoperative tumor recurrence, which provided preliminary experimental basis for hypothesis of “tumor-phlegm microenvironment”. Objective: To explore a method of extracting tumor interstitial fluid (TIF) which is similar to muddy phlegm in Chinese medicine (CM), interleukin-8 (IL-8) in concentration was taken as the representative of the content of TIF, analyzed in the extracted TIF and the original tumor tissue, and examined to see whether TIF has an interfering effect on tumor recurrence. Tumor tissue-bearing ground, centrifuged, and filtered for intercellular substances. Tumor-bearing Kunming S180 mice were raised for 21 days and then the tumors were removed to observe the influence of intervention with TIF, normal saline (NS) and a blank control on tumor recurrence. Results: The content of IL-8 in the filtered and unfiltered tumor tissues was not significantly different (P> 0.05 ) Postoperative tumor recurrence in TIF intervention group was significantly higher than that in the NS intervention and control groups (60%, 12/20 vs. 20%, 4/20 vs. 15%, 3/20, χ2 = 11.058, P <0.01). Tumor cells grew vigorously and Large numbers of tumor cells were seen necrotic in the NS intervention group, and small numbers of tumor cells were seen necrotic in the blank control group. Conclusions: TIF can be effectively extracted by the means described. It does not contain tumor cells, but its contents such as IL-8 may stimulate tumor cell growth and promote postoperative tumor recurrence, which provides preliminary experimental basis for hypothesis of “tumor-phlegm microenvironment ”.