Abstract: The diffusion behavior between U-10Mo and Al-Si alloys was studied with diffusion-couple method. The couple was annealed in a high vacuum heat-pressure furnace at 555, 570, 580, 590 and 595 ℃, respectively for 5-10 h. Annealing conditions have a significant effect on interaction-layer thickness. When temperature is lower than 580 ℃ with pressuring, the thickness suddenly decreases then slowly increases with the Si content increasing; however, when temperature is higher than 580 ℃ the thickness increases with the Si content increasing. Interaction layer with higher Si content which thickness is lower than that with lower Si content is composed of three layers. Si-rich layer with the composition of (U, Mo)(Al, Si)_x (x≤3) closes to U-10Mo side, Si-poor layer with the composition of (U, Mo)(Al, Si)_x (x＞3) closes to Al-Si side.