I just got the test result of my 4.5 yrs old, his WPPSI-IV score is not in the gifted range (a bit lower than 130) but his WJ-IV score is in very superior range, however, we did not finish the full test as he was so tired at that time (he did the WJ-IV test after WPPSI-IV) and the examiner think it is time to stop it.

I found that the criteria of applying for Davidson young scholar using WJ-IV is
Standard score 145+ on
General Intellectual Ability (GIA)
OR
Standard score 145+ on at least two of the following:
Broad Reading
Broad Math
Broad Written Language
Total Achievement

However, i can't find these terms in the report, He got these two> 145 in Cluster/Test
Academic skills, Mathematics
and got these two > 145 on specific subtests
Applied Problems, Calculation

is the result enough for applying Davidson young scholars? or I should have him done a full test again when he is 5?

Thanks a lot!

No, that is not enough, according to the criteria listed. You do not have GIA results, because the achievement portion of the WJ-IV was used, not the cognitive portion (that would have duplicated the WPPSI-IV data). You also do not have enough Cluster scores, since only Mathematics is a high enough score. There is no Broad Mathematics score because Math Facts Fluency was not administered (because of his age).

Thanks! Seems I have to ask for testing him again in order to apply for Davidson young scholar.

You can't apply until he is 5, anyway (although you can have testing done before that and use it for his application as long as it is not more than two years old, IIRC).