As a promising technology, blockchain has widespread application in many decentralized systems. However, scalability is still a major challenge to blockchain adoption.Sharding is a promising method for scaling blockchain. However, in current implementations, the complexity of cross-shard transactions and the imbalance of shard workloads have become key factors hindering its potential performance advantages. We propose ALB-Chain, a meticulously designed blockchain system aimed at achieving exceptional scalability and balancing the workload across all shards. In ALB-Chain, we introduce a replica account mechanism, which transforms cross-shard transactions into intra-shard transactions, thereby enhancing transaction throughput. Additionally, we introduce a lightweight Account Aggregation Model (AAM), which supports batch aggregation and threshold signatures. To optimize system performance and ensure balanced workload distribution among shards, we have specially designed a dynamic partitioning algorithm named MLPA. This algorithm intelligently monitors the operational status of each shard and dynamically adjusts task allocation among shards based on historical data, ensuring that the entire system maintains high efficiency and stability. We conducted transaction-driven simulations using real Ethereum transaction datasets. The evaluation results demonstrate that the proposed protocol outperforms other benchmarks in terms of throughput, transaction processing latency, transaction queue size, and shard workload distribution.