diff --git a/python/taichi/ui/canvas.py b/python/taichi/ui/canvas.py
index 8d7721d047cf7..d9e3da3689bdd 100644
--- a/python/taichi/ui/canvas.py
+++ b/python/taichi/ui/canvas.py
@@ -111,7 +111,9 @@ def circles(self,
         Args:
             centers: a taichi 2D Vector field, where each element indicate the \
                 3D location of a vertex.
-            radius (float): radius of the circles, relative to the height of the screen.
+            radius (Union[float, numpy.array]): radius of the circles in pixels. \
+                Can be either a single number, which will be applied to all circles, or a 1D NumPy array of the same length as `centers`.\
+                The `i-th` item in the array will be the radius for the `i-th` circle in `centers`.
             color: a global color for the triangles as 3 floats representing \
                 RGB values. If `per_vertex_color` is provided, this is ignored.
             per_vertex_color (Tuple[float]): a taichi 3D vector field, where \
diff --git a/python/taichi/ui/gui.py b/python/taichi/ui/gui.py
index ddbc99dbb047d..a2dad1dc8d30f 100644
--- a/python/taichi/ui/gui.py
+++ b/python/taichi/ui/gui.py
@@ -362,7 +362,9 @@ def circles(self,
 
         Args:
             pos (numpy.array): The positions of the circles.
-            radius (Number, optional): The radius of the circles in pixel. Default is 1.
+            radius (Union[Number, numpy.array], optional): The radius of the circles in pixel. \
+                Can be either a number, which will be applied to all circles, or a 1D NumPy array of the same length as `pos`. \
+                The default is 1.
             color (int, optional): The color of the circles. Default is 0xFFFFFF.
             palette (list[int], optional): The List of colors from which to
                 choose to draw. Default is None.