pushbotton1是畫圖的，pushbutton2是清除的，你要做一個數據傳遞的工作，因為callback中的變數都是區域性變數：

function pushbutton1_Callback(hObject, eventdata, handles)

% hObject handle to pushbutton1 (see GCBO)

% eventdata reserved - to be defined in a future version of MATLAB

% handles structure with handles and user data (see GUIDATA)

a=0:0.01:pi;

ax1=SUBPLOT(2,1,1);plot(a,sin(a));

ax2=SUBPLOT(2,1,2);plot(a,cos(a));

setappdata(handles.pushbutton1,"ax1",ax1)

setappdata(handles.pushbutton1,"ax2",ax2)

% --- Executes on button press in pushbutton2.

function pushbutton2_Callback(hObject, eventdata, handles)

% hObject handle to pushbutton2 (see GCBO)

% eventdata reserved - to be defined in a future version of MATLAB

% handles structure with handles and user data (see GUIDATA)

ax1=getappdata(handles.pushbutton1,"ax1");

ax2=getappdata(handles.pushbutton1,"ax2");

cla(ax1)

cla(ax2)