The world's biggest EV seller, known for its focus on budget models priced under 150,000 yuan ($A30,600), is under pressure from rivals including Geely and Leapmotor.
BYD's first-quarter net profit dropped 55.4 per cent from a year earlier to $US599.46 million ($A836.67 million), deepening a 38.2 per cent fall in the fourth quarter, the data showed.
Revenue fell 11.8 per cent, extending a declining streak to a third straight quarter.
"BYD needs domestic sales volumes to pick up sequentially in Q2 and see a more sustained rebound and market share recovery in Q3 for overall profits to improve," said Eugene Hsiao, head of China equity strategy at Macquarie Capital.
Pressure has mounted as China scales back trade-in subsidies for entry-level electric cars and plug-in hybrids.
BYD's overall sales declined for a seventh straight month in March despite sustained strong growth in overseas shipments.
As its domestic sales face a prolonged slump, BYD is aggressively targeting international markets with a focus on advanced technology or manufacturing localisation.
The biggest Chinese competitor to Tesla has said it is confident of reaching its 2026 overseas sales target of 1.5 million vehicles or even higher, implying growth of more than 40 per cent from 2025 although it has not disclosed an overall sales target.
Vincent Sun, an analyst at Morningstar, projected BYD's exports would rise 25 per cent to 30 per cent this year while total vehicle sales are expected to grow about 12 per cent.
However, Hsiao said overseas sales may not be enough to fully offset domestic weakness if current sales trends continue.
Seeking to regain its technological edge, BYD is doubling down on ultra-fast charging technology, aiming to lure drivers loyal to petrol-powered cars by easing charging time concerns.
BYD kicked off pre-sales for its Datang full-size electric SUV at the Beijing car show on Friday, joining a growing list of Chinese car makers targeting the higher-end segment and stepping up competition with European premium brands.
