As the error states, The function interp1() expects the length of the first input to be equal to the number of rows in the second input.
To achieve that, you can transponse 't' -
h=6:2:18; %一个1*7的double
t=[18,20,22,25,30,28,24;15,19,24,28,34,32,30]; %一个2*7的double
x=6.5:2:17.5; %一个1*6的double
%Transposing t
t = transpose(t);
%Interpolation
y=interp1(h,t,x,'spline')
