Trust is a fundamental concern in Grid environment. In this paper, we focus on the behavior trust that varies with time. Because of the fuzzy nature of trust, it is more appropriate to adopt fuzzy logic to express and compute trust than adopt probabilities approach. A new behavior trust model based on fuzzy-logic in Grid environment is proposed. By variable weighted fuzzy comprehensive evaluation, Direct Trust can be gotten; by derivation and combination of trust, Reputation can be obtained. Expert's experience is used to set and simplify fuzzy rules. Malicious recommendation in trust transmission process are also be removed and punished in this model. Simulation results show that entities in Grid can use resources or deploy services more securely in the support of this fuzzy trust model.

<span style="font-size: 10pt; font-family: &quot;Times New Roman&quot;; mso-fareast-font-family: 宋体; mso-ansi-language: EN-US; mso-fareast-language: EN-US; mso-bidi-language: AR-SA; mso-bidi-font-size: 9.0pt;" lang="EN-US">Trust is a fundamental concern in Grid environment. </span><span style="font-size: 10pt; font-family: &quot;Times New Roman&quot;; mso-fareast-font-family: 宋体; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA; mso-bidi-font-size: 9.0pt;" lang="EN-US">B</span><span style="font-size: 10pt; font-family: &quot;Times New Roman&quot;; mso-fareast-font-family: 宋体; mso-ansi-language: EN-US; mso-fareast-language: EN-US; mso-bidi-language: AR-SA; mso-bidi-font-size: 9.0pt;" lang="EN-US">ehavior trust that varies with time</span><span style="font-size: 10pt; font-family: &quot;Times New Roman&quot;; mso-fareast-font-family: 宋体; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA; mso-bidi-font-size: 9.0pt;" lang="EN-US"> is indispensable in the trust system</span><span style="font-size: 10pt; font-family: &quot;Times New Roman&quot;; mso-fareast-font-family: 宋体; mso-ansi-language: EN-US; mso-fareast-language: EN-US; mso-bidi-language: AR-SA; mso-bidi-font-size: 9.0pt;" lang="EN-US">. Because of the fuzzy nature of </span><span style="font-size: 10pt; font-family: &quot;Times New Roman&quot;; mso-fareast-font-family: 宋体; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA; mso-bidi-font-size: 9.0pt;" lang="EN-US">b</span><span style="font-size: 10pt; font-family: &quot;Times New Roman&quot;; mso-fareast-font-family: 宋体; mso-ansi-language: EN-US; mso-fareast-language: EN-US; mso-bidi-language: AR-SA; mso-bidi-font-size: 9.0pt;" lang="EN-US">ehavior trust,</span><span style="font-size: 10pt; font-family: &quot;Times New Roman&quot;; mso-fareast-font-family: 宋体; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA; mso-bidi-font-size: 9.0pt;" lang="EN-US"> </span><span style="font-size: 10pt; font-family: &quot;Times New Roman&quot;; mso-fareast-font-family: 宋体; mso-ansi-language: EN-US; mso-fareast-language: EN-US; mso-bidi-language: AR-SA; mso-bidi-font-size: 9.0pt;" lang="EN-US"><span style="mso-spacerun: yes;">&nbsp;</span>it is more appropriate to adopt fuzzy logic to express and compute trust</span><span style="font-size: 10pt; font-family: &quot;Times New Roman&quot;; mso-fareast-font-family: 宋体; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA; mso-bidi-font-size: 9.0pt;" lang="EN-US">s</span><span style="font-size: 10pt; font-family: &quot;Times New Roman&quot;; mso-fareast-font-family: 宋体; mso-ansi-language: EN-US; mso-fareast-language: EN-US; mso-bidi-language: AR-SA; mso-bidi-font-size: 9.0pt;" lang="EN-US"> </span><span...