East China Regional Electricity Market, the first regional electricity market in China, will adopt the structure of Broker spot market combined with bilateral contracts. The conventional transactions scheduling method of using Broker-matching algorithm cannot obtain optimal economic benefit with considering network constraints. This paper proposes a new transaction scheduling method of considering network constraints directly. With introducing the generation contribution factor and load-extracting factor, the problem of coordination of multi-level electricity market is solved. In consideration of the characteristic of bilateral transaction, a mathematical model is established for transaction scheduling in Broker trading system of regional electricity market with transaction matrix as a mathematical representation. The results of the test on IEEE 30 bus system show that the model corresponds with the features of Broker trading mode without considering network constraints, and can obtain optimal economic benefit with considering network constraints. The effectiveness of the method is proved.