Some urine tests indicates trace hematuria and trace protein but hpf shows 0-3 RBC and wbc, others show no trace, what can it be?

Nonspecific. Microscopic hematuria can indicate anything from a benign entity to stones to BPH to bladder or kidney cancer. It needs to be further evaluated.
This is common. Anyone can have trace proteinuria intermittently; some people get heavier proteinuria just from standing. A bit of blood or blood-like reactivity can happen from playing sports (a bit of myoglobin in the urine), from a few disrupted capillaries from riding a bicycle, or a variety of other life events. If your physician is not concerns, i would not be either.