Cross-domain recommendation (CDR) addresses data sparsity and cold-start challenges in recommendation systems.Behavior importance-aware Graph Neural Architecture Search (BiGNAS) is proposed to optimize GNN architecture and data importance for CDR.BiGNAS uses a Cross-Domain Customized Supernetwork to search the optimal GNN architecture without retraining.The Graph-Based Behavior Importance Perceptron dynamically assesses the importance of source domain behaviors for improved recommendations.