Acquiring the firing sequence of neurons located in varying depths with cellular resolution is essential to understand the underlying functional neural circuits of living animals. Light-sheet fluorescence microscopy (LSFM) enables neuronal activities recording with high temporal and spatial resolutions. However, constrained by the single-plane illumination and detection configuration, neurons located in varying depths are impossible to be recorded simultaneously. To address this challenge, we develop the simultaneous multi-plane imaging light-sheet fluorescence microscopy (SIMPLE-LSFM) by combining multi-plane or region-of-interest illumination of a sample, and spherical-aberration-assisted point spread function in detection space for simultaneous imaging of different depth within a sample. SIMPLE-LSFM is demonstrated by acquiring neuronal activities of six depths simultaneously in the larval zebrafish; while keeping cellular resolution, millimeter-scale field of view, and > --> 100 H z temporal resolution. Firing sequences of the neurons located in varying depths were successfully captured. The SIMPLE light-sheet methods enable high-speed cellular-resolution multi-depth-resolved mapping of anatomic structure and fast dynamics in three dimensions.