你的版本是什么？19a好像不能复现你的结果。下边的代码的结果与加不加hold on之后的语句无关。
figure
0 y! ^2 A2 a3 ]% P1 \x = linspace(-2*pi,2*pi);
; i: n2 T6 o, t- o, [y = linspace(0,4*pi);
[X,Y] = meshgrid(x,y);
Z = sin(X) + cos(Y);
contourf(X,Y,Z,10)

hold on
x = linspace(-2*pi,2*pi);
2 g) z+ I, J8 c9 o. i% qy = linspace(0,4*pi);
/ B7 s6 S5 @. j/ O  ~- ~% x[X,Y] = meshgrid(x,y);
* E/ L6 X& p) ?) wZ = sin(X)+cos(Y);
contour(X,Y,Z)
+ o: P6 M1 r1 E. `7 B+ Nhold off