Authorities wheeled out giant furnaces to incinerate some of the massive haul on display, including nearly half a tonne of methamphetamine, 190,000 ecstasy tablets and 420 kilogrammes (926 pounds) of marijuana.
Widodo and other top officials, wearing protective gloves and masks, inspected the drugs before tossing bags of pills into the incinerator.
Indonesia has tough drugs laws but Widodo has made combating narcotics a top priority since taking office in late 2014, resuming the execution of traffickers after an unofficial hiatus.
Widodo has defended his hardline stance, claiming Indonesia faces a "drugs emergency" and must act to protect the next generation.
"Every year 15,000 Indonesian youth die because of drugs. How many drug dealers and traffickers die every year?" he said.
"When I see this evidence, it becomes clear we once again have to declare a war on drugs," he added, to applause.
Indonesia's drugs agency said in 2016 nearly a tonne of methamphetamine, three tonnes of marijuana and roughly 600,000 ecstasy pills had been seized.
Widodo ordered an official investigation in August into allegations top police and military officers took kickbacks from a drug kingpin to protect his lucrative business.
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