[winndy]

I think I figured it out.

idaapi.i

change

%array_class(uchar, uchar_array);

to

%array_class(unsigned char, uchar_array);

recompile idapython,then call it in python like this:

func = idaapi.get_func(idaapi.get_screen_ea())

patternlen = 3
pattern = idaapi.uchar_array(patternlen)
pattern[0] = 0x18;
pattern[1] = 0x00;
pattern[2] = 0x89;

print pattern

mask = idaapi.uchar_array(patternlen)
mask[0] = 0xFF
mask[1] = 0xFF
mask[2] = 0xFF

print mask

ea = idaapi.bin_search(func.startEA,func.endEA,pattern,mask,patternlen,idaapi.BIN_SEARCH_FORWARD,idaapi.BIN_SEARCH_NOCASE)

print '%08lx'%(ea)