Ferrari held a sizeable advantage over the Silver Arrows at the last round in Bahrain, with emerging star Charles Leclerc cruelly denied a win following a late engine failure.
But although Sebastian Vettel topped the time sheets in Friday's first session at Formula One's 1,000th race, Bottas put his Mercedes on top in the second running.
— Formula 1 (@F1) April 12, 2019
Lewis Hamilton finished a distant fourth after a scruffy afternoon in which the Mercedes star spun on his first lap. He ended the day seven tenths off his team-mate's pace.
Hamilton has built a fanatical support base in China after winning here five times. A plethora of British flags adorned the main grandstand, but his army of fans did not get to see him dominate the session.
Indeed, his spin at the third bend was something of a rarity for the usually error-free world champion.
Max Verstappen suggested it could be a three-team battle in Sunday's 56-lap race after he finished third in his Red Bull, just 0.221 seconds slower than Bottas.
— Mercedes-AMG F1 (@MercedesAMGF1) April 12, 2019
Leclerc indicated he could be a title contender in Bahrain, but was behind Vettel in both sessions. He was a quarter-of-a-second down on his team-mate on Friday morning, and finished seventh later in the day.
The Monegasque was restricted to only 13 laps, 20 fewer than Vettel, after he suffered a mechanical issue which brought his running to a premature end.
Lando Norris delivered McLaren's best finish in more than a year with his fine drive to sixth last time out, and the British team will be encouraged by their showing here.
Norris, the 19-year-old Briton, was eighth, two places behind his McLaren team-mate Carlos Sainz.
Another of Britain's rookies, George Russell, endured another testing day in his formative Formula One career.
The Englishman, in his woefully uncompetitive Williams, was the slowest driver in both 90-minute sessions, finishing the best part of three seconds behind Bottas.