The mobile agent technology plays an important role in electronic commerce. However, security issues need to be tackled. Some schemes have been proposed to protect the private key of the agent's owner, but seldom pay attention to the abuse of the information in the agent. Threshold proxy signature scheme can be applied for avoiding the abuse of the information in the agent. However, most existing proxy signature schemes are not available for mobile agent-based electronic transactions because they have some disadvantages of the security and stability. A new threshold proxy signature scheme for the mobile agent-based electronic transactions is proposed in this paper. In the proposed scheme, the owner's private key is secure, and the information in mobile agents is protected as well because of the distribution of the information. With security and property analysis, we show that the scheme is secure and practical for mobile agent-based electronic transactions.