Austenitic stainless steel small-diameter tubes, with their thin walls, generate multiple echoes due to ultrasonic wave reflections and mode transitions at the interfaces, leading to significant artifacts in phased array imaging that hinder defect detection. To address the impact of ultrasonic mode type, number, and their amplitude spatial variability on multimodal compound imaging performance, this paper proposes a multimodal ultrasonic total focus compound imaging method with spatial compensation for defect response. A defect spatial response model is developed, and compound imaging is performed on the full matrix data acquired using this model, which shows good agreement with results from CIVA simulation software. The defect response values, determined by maximum intensity near the defect in each imaging mode, are compared, with deviations within ±3 dB relative to the simulation. Additionally, the spatial distribution of imaging sensitivity in different modes is analyzed, and spatial compensation parameters suitable for each mode are identified. Compound imaging is carried out using both calibrated direct modes and half-skip modes. Compared to single-mode imaging and direct-sum composite imaging, the proposed method, based on defect spatial response compensation, achieves higher defect amplitude and reduced artifact amplitude, with no artifacts in imaging results of circular-hole defects at various positions. The method is further applied to crack and porosity defect experiments, where it effectively suppresses artifacts and enhances the signal-to-noise ratio compared to single-mode imaging.